Perpendicular Magnetic Anisotropy Of (Co/Pd) Multilayers
sensorsArticleEffect of Composition and Thickness on thePerpendicular Magnetic Anisotropy of(Co/Pd) MultilayersBharati Tudu 1,2 , Kun Tian 1 and Ashutosh Tiwari 1, *12*Department of Materials Science and Engineering, University of Utah, Salt Lake City, UT 84112, USA;bharati.tudu@jadavpuruniversity.in (B.T.); cindy.tian@utah.edu (K.T.)Department of Physics, Jadavpur University, Kolkata-700032, IndiaCorrespondence: tiwari@eng.utah.edu; Tel.: 1-801-585-1666Received: 2 November 2017; Accepted: 22 November 2017; Published: 28 November 2017Abstract: Magnetic materials with perpendicular magnetic anisotropy (PMA) have wide-rangingapplications in magnetic recording and sensing devices. Multilayers comprised of ferromagneticand non-magnetic metals (FM–NM) are interesting materials, as their magnetic anisotropy dependsstrongly on composition and growth parameters. In this context, (Co/Pd) multilayers have gainedhuge interest recently due to their robustness and tunable PMA. Here, we report a systematic study ofthe effect of composition on the magnetic anisotropy of (Co/Pd) multilayers grown by Direct Current(DC) magnetron sputtering. Four different series of (Co/Pd) 10 multilayers with different thicknessesof Co and Pd were examined. Vibrating sample magnetometery was used to determine the magneticanisotropy of these films. X-ray diffraction and transmission electron microscopy experiments wereperformed to understand the structural morphology of the films. Our results showed that (Co/Pd) 10multilayers exhibit PMA when the Co to Pd ratio is less than or equal to 1 and the thickness of Colayers is not more than 5 Å. Maximum effective anisotropy energy is shown by the films with a Co toPd ratio of 1/3.Keywords: perpendicular magnetic anisotropy; sputtering; multilayers; magnetic tunnel junctions1. IntroductionMagnetic sensors have been applied to almost every sector of technology, as well as in ourday-to-day life. In the last few years, sensors based on spintronics have gained particular attentiondue to their numerous advantages such as low power consumption, high sensitivity, compactness,and CMOS compatibility [1–3]. Materials with perpendicular magnetic anisotropy (PMA) are veryinteresting in this regard compared to in-plane anisotropy materials due to their ability to provide betterstorage density and thermal stability [4,5]. PMA magnetic media have already succeeded the in-planemedia in hard disks [6]. In magnetoresistive random access memories (MRAM) also, PMA materialshave performed better. With the discovery of the spin transfer torque (STT) phenomenon, a hugerevolution has occurred in the MRAM industry [7–9]. Using the STT phenomenon, the magnetizationstate (‘0’ or ‘1’) of the free layer, which is used to store information in a magnetic tunnel junction (MTJ),can be reversed with a spin polarized current. This makes the MRAM device simpler, faster, low powerconsuming, and more efficient compared to the conventional field-induced MRAM. Till now, materialswith in-plane anisotropy have been practically used in STT-MRAM [10]. However, PMA materials canprovide superior STT-MRAM properties such as excellent thermal stability, lower power consumption,and increased storage density, which can take the MRAM technology below the 10 nm node [11].Different categories of PMA materials have been studied for the perpendicular MTJ (p-MTJ),such as rare earth-transition metal films like GdFeCo or TbFeCo, L10 ordered FePt or CoPt films,Sensors 2017, 17, 2743; doi:10.3390/s17122743www.mdpi.com/journal/sensors
Sensors 2017, 17, 27432 of 12Heusler alloys such as Mn3-δ Ga, CoFeB alloys, and ferromagnetic/non-magnetic metal multilayerssuch as Co/Pt, Co/Pd, Co/Au, Fe/Pt, and Fe/Pd [4,5]. For their possible application in STT-MRAM,in addition to their high perpendicular anisotropy, these materials should also have high spinpolarization, high tunneling magnetoresistance (TMR), low gilbert damping constant (α), and highthermal stability. In this context, Co-based multilayers are promising candidates due to their tunablePMA, spin-polarization, and α values [12–14]. In these multilayers, the sharp interfaces betweenthe magnetic and non-magnetic lattices, as well as the strain in the magnetic layer, leads to thehybridization of the magnetic metal’s 3d and non-magnetic metal’s 5d orbitals, which thereby increasesthe perpendicular magnetic moment of the magnetic layer and gives rise to PMA [15–17]. With theincrease in the number of sharp interfaces, the PMA gets stronger. For using such multilayer filmsin p-MTJ for STT-MRAM application, there are some specific requirements. These requirementsare driven by the need for higher TMR, higher thermal stability ( ), and a lower switching current(Ic ) needed for switching the magnetization of the free layer. High thermal stability demands largeeffective magnetic anisotropy energy, Keff , and a low switching current demands smaller values ofthe thickness, volume, magnetization, anisotropy field, and damping parameters of the free layer [4].Also, the coercivity of the reference or fixed layer of the p-MTJ needs to be much higher than the freelayer to ensure reliable preservation of data in the free layer against thermal fluctuation. Thus, properknowledge of the Co-based multilayer system is needed for employing it as the reference layer and freelayer in a p-MTJ. It is well established that Co/Pd multilayer can show PMA with Co film thickness 1 nm [15–18]. As the Co layer gets thicker than this, the system becomes magnetized in the in-planedirection dominated by the shape anisotropy [15]. However, not much studies have been done on theCo/Pd compositional dependence on the PMA.In this study, we report a systematic investigation of magnetic anisotropy in Co/Pd multilayersdeposited by Direct Current (DC) magnetron sputtering. Different series of Co/Pd multilayers werestudied to understand the effect of the composition and thickness of the Co and Pd layers on theoverall magnetic properties. The magnetic, structural, and compositional studies were performedusing vibrating sample magnetometer (VSM), X-ray diffraction (XRD), high-resolution transmissionelectron microscopy (HR-TEM), and Energy-dispersive X-ray spectroscopy (EDS).2. Materials and MethodsFour different series of (Co/Pd) multilayers with stack structure Pd3 /(CotCo /Pd0.3 or 0.9 ) 10 /Pd3with tCo values ranging from 0.1 to 0.8 nm and Pd3 /(Co0.2 or 0.4 /PdtPd ) 10 /Pd3 with t Pd values rangingfrom 0.1 to 1.8 were deposited on Si substrate by Direct Current (DC) magnetron sputtering at roomtemperature. The numbers in the subscript denote the thickness in nanometer. The 3 nm thick bottomPd layer was used as a seed layer for (111) growth direction. The deposition chamber (Denton 635Sputter system) was first evacuated to a base pressure of 6 10 7 Torr. Depositions were carriedout at a constant Ar pressure of 5 mTorr using Ar flow rate of 35 sccm. Low deposition rates forboth Co (0.093 Å/s) and Pd (0.151 Å/s) were used to ensure uniform growth of the films with sharperinterfaces and less Co-Pd intermixing [19]. The deposition rate of Co was 0.093 Å/s and that of Pdwas 0.151 Å/s, corresponding to a power of 10 W and 6 W, respectively, for all the samples. After thedeposition, the magnetization hysteresis loops in the in-plane and out-of-plane magnetic fields weremeasured using a Microsense FCM-10 vibrating sample magnetometer (VSM). After subtracting thediamagnetic contribution from the substrate, the effective anisotropy, Keff , was calculated from the areaenclosed between the easy and hard axis of the M-H curves [18]. The saturation magnetization perunit volume was calculated by dividing the magnetic moment by the total volume of the (Co/Pd) 10multilayer [20]. The multilayer volume is obtained by multiplying the sample area with the totalmultilayer thickness. The error in the absolute values of the saturation magnetization was estimatedto be approximately 10% and was mostly due to the uncertainty in determining the thicknesses ofthe layers. For structural characterization of the films, we performed XRD studies using a Bruker D2Phaser X-ray Diffractometer with Cu-Kα radiation. A high-resolution JEOL 2800 S/TEM system was
Sensors 2017, 17, 27433 of 12system was used for performing transmission electron microscopy (TEM) and energy dispersivespectroscopy(EDS) on selected samples.Sensors 2017, 17, 27433 of 123. Results and Discussionused for performing transmission electron microscopy (TEM) and energy dispersive spectroscopy(EDS) on selected samples.3.1. Effect of Co Thickness3. Results and DiscussionTo understand the effect of Co thickness on the magnetic properties of Co/Pd multilayers, twoEffect of Coseries of3.1.samples,oneThicknesswith thinner Pd layer [(CotCo /Pd0.3) 10: series 1] and other with thicker Pd layereffectof Co thicknesson the magneticpropertiesmultilayers, two 10:understandseries 2], thewereprepared.The thicknessof cobaltlayer,of tCo/Pd[(CotCo /Pd0.9)ToCo , used was 0.1, 0.3, 0.4, 0.5,series of samples, one with thinner Pd layer [(CotCo /Pd0.3 ) 10 : series 1] and other with thicker Pd layer0.6, and 0.8 nm. Figure 1a,b shows the XRD pattern of the films for the series 1 and 2. From the XRD[(CotCo /Pd0.9 ) 10 : series 2], were prepared. The thickness of cobalt layer, tCo , used was 0.1, 0.3, 0.4, 0.5,data, it canbe seenthatfor series2, allthethethreesamplesshowfora thepeakaround40.4 correspondingto0.6, and0.8 nm.Figure1a,b showsXRDpatternof the filmsseries1 and 2.Fromthe XRD fcc (111)data,crystalorientation.peak40.4 a peakshiftsaroundtowardshigher θ valueswithit can beseen that for Theseries(111)2, all thethreearoundsamples show40.4 correspondingto fcc (111)crystal orientation.around 40.4shiftstowardshigher θ valueswith(Co/Pd)increasingincreasingCo thickness,whichThecan(111)be peakattributedto thelatticecontractionof thesystem ractionofthe(Co/Pd)systemtomatchthematch the lattice structure of the fcc Co layer. In contrast, no preferred crystal orientation was seenlattice structure of the fcc Co layer. In contrast, no preferred crystal orientation was seen for the series 1for the series1 samples, which can be attributed to the thinner Pd layer. The thicker Pd layer facilitatessamples, which can be attributed to the thinner Pd layer. The thicker Pd layer facilitates the multilayerthe multilayergrowth along (111) direction.growth along (111) direction.Figure 1. X-ray diffraction (XRD) (θ-2θ) patterns corresponding to samples of (a) series 1 and (b) series 2.Figure 1. X-ray diffraction (XRD) (θ-2θ) patterns corresponding to samples of (a) series 1 and (b) seriesA small peak at 39.5 corresponds to the substrate.2. A small peak at 39.5 corresponds to the substrate.The magnetization curves for these two series of samples measured along the in-plane andTheout-of-planemagnetizationcurvesfor thesetwo2 andseriesof samplesalongin-planedirectionare shownin Figures3. Thesaturation measuredmagnetizationof thethefilmsincreases and outof-planewithdirectionare shownFigureswhich2 andis 3.Thesaturation magnetizationfilmsthe increasein the Cointhickness,quiteunderstandable,since the amountofoftheCo luesofthesesamplesarelistedinTable1.with the increase in the Co thickness, which is quite understandable, since the amount of Co per unitvolume increases. The magnetization values of these samples are listed in Table 1.Table 1. Magnetization values of series 1 [(CotCo /Pd0.3 ) 10 ] and series 2 [(CotCo /Pd0.9 ) 10 ] samplescorresponding to different values of tCo .Table 1. Magnetization values of series 1 [(CotCo /Pd0.3) 10] and series 2 [(CotCo /Pd0.9) 10] samplescorrespondingto differentvalues tof (nm)tCo .Serial No.Co Thickness,CoSerialNo.123456Co 1Thickness,t2Co (nm)34 0.15 0.360.40.50.60.8Saturation Magnetizationfor Series 1 (emu/cm3 )0.1Saturation Magnetization3500.3700 3)Series 1 (emu/cm0.4800350 8750.50.6700 9330.810188008759331018forSaturation Magnetizationfor Series 2 (emu/cm3 )Saturation140 Magnetization for350Series2 (emu/cm3)431140500560350659431500560659
Sensors 2017, 17, 2743Sensors 2017, 17, 2743Sensors 2017, 17, 27434 of 124 of 124 of 12Figure2. 2. In-plane(blacksquare)out-of-plane(red magneticcircle) magnetichysteresisforFigureIn-plane rcle)hysteresisloopsloops forfor thetheloopssampleFigure2. In-planesquare)andout-of-plane(redmagnetic hysteresissamplethe d)0.1/Pd0.3) 10,0.1(b) (Co/Pd 0.310) 10, (d) (Co0.3) 10, (e) (Co0.6/Pd, (f)(Co0.10.3 0.3 /Pd10 0.3) 10, (c)0.3(Co0.40.30.40.5/Pd0.3 100.5 0.3) 100.3 10 ,/Pd0.3) 10, (b) (Co0.3/Pd0.3) 10, (c) (Co0.4/Pd0.3) 10, (d) (Co0.5/Pd0.3) 10, (e) (Co0.6/Pd0.3) 10, (f)(a) (Co(e) (Co0.6/Pd, (f) (Co0.8/Pd0.30.3 10) of10seriesseries1. 0.8 /Pd0.3 ) 10 of series 1./Pd0.3)) 10of1.(Co0.8Figure 3.3. In-plane (black(black square)square) andand out-of-planeout-of-plane (red(red circle)magneticmagnetic hysteresishysteresisloopsloops forfor thethe samplesampleFigureFigure3. In-planeIn-plane (blacksquare) andout-of-planecircle)(red circle) magnetichysteresisloops for0.1/Pd0.9) 10, (b) (Co0.3/Pd0.9) 10, (c) (Co0.4/Pd0.9) 10, (d) (Co0.5/Pd0.9) 10, (e) (Co0.6/Pd0.9) 10, (f)(a)(Co) 10, 0.1(b)0.3/Pd0.9) 10, (c) (Co0.4/Pd0.9) 10, (d) (Co0.5/Pd0.9) 10, (e) (Co0.6/Pd0.9) 10, (f)(Co0.1/Pdthe(a)sample(a)0.9(Co/Pd(Co0.9 ) 10 , (b) (Co0.3 /Pd0.9 ) 10 , (c) (Co0.4 /Pd0.9 ) 10 , (d) (Co0.5 /Pd0.9 ) 10 ,(Co0.80.8/Pd0.9) 10 of series 2.(Co/Pd0.9) 10 of series 2.(e) (Co0.6 /Pd0.9 ) 10 , (f) (Co0.8 /Pd0.9 ) 10 of series 2.Using thethe magnetizationmagnetization data,data, effectiveeffective anisotropyanisotropy energiesenergies (K(Keffeff)) forfor allall thethe samplessamples isotropyenergies(K)forallthesampleswerecalculated. FigureFigure 4a4a showsshows thethe plotplot ofof KKeffeff withwith thethe thicknessthickness ofof CoCoefflayer.layer. AA positivepositive KKeffeff valuevaluecalculated.describesFiguresystemwith theout-of-planepreferreddirection ofofComagnetization(or PMA),PMA),whereascalculated.4a showsplot of Keffpreferredwith the thicknesslayer. A positiveKeff valuedescribesdescribesaa hereasaanegativeKeff em.ItcanbeseenthatPMAisobtainedina ,whereasanegativeKnegative Keff value describes an in-plane magnetized system. It can be seen that PMA is obtained in effvalue describes an in-plane magnetized system. It can be seen that PMA is obtained in some samples of
contribution from both the volume and interface, which follows the relation [18]:Keff Kv 2Kst(1)where Kv is the volume anisotropy, Ks the interface anisotropy, and t the thickness of the magneticSensors2017, 17, 2743layer.5 of 12The interface anisotropy, which is mainly responsible for the PMA, can be found for a multilayerof particular Pd thickness by plotting the Keff tCo as a function of tCo and calculating the interceptbothseries1 and series 2. Series 1 samples with thinner Pd layer (0.3 nm) lose PMA substantially with( 2Ks) from the curve [18–22]. Figure 4b shows the plot of Keff tCo with tCo for the two differenttheseries.increaseof Colayerthatthickness,PMA isup to theCoitsthicknessof 0.3 nmonly.Series 2It canbe seenfor bothandthe series,Keffobtained tCo ckerPd layercomparativelyhigherPMA,andbePMAup tobelow withthe Cothicknessof 0.3(0.9nmnm)and show0.4 nm,respectively. Thiseffectcoulddue isto obtainedthe coherentthe(uniformCo canbeattributedtotheenhancedlattice strain in the layer) and incoherent growth respectively below and above a criticalPMA[21]. arly, theKsvolumeand frominterfaceweremagneticthicknessThe interfaceanisotropy,, calculatedthe anisotropiesintercept of the22calculatedtheseerg/cmtwo series.The effectiveanisotropyenergyhascontribution whichfrom boththe volumelinear fit,foris 0.117and 0.085erg/cm forseries 1 andseries2, respectively,is comparabletointerface,the valueswhichreportedfor sputteredCo/Pdmultilayers [15–18]. The volume anisotropy, Kv, is foundandfollowsthe relation[18]:to be 6.78 106 erg/cm3 for series 1 and 3.37 106 erg/cm3 for series 2. The comparatively lower volumeKsanisotropy of series 2 samples helps the systemKe f f toKfavorv 2 PMA up to a Co thickness of 0.5 nm. Beyond(1)t hand, for the series 1 samples, this critical0.5 nm, the system prefers in-plane anisotropy. On the otherthicknessof Cois onlyanisotropy,0.3 nm, beyondthe systemprefersanisotropy.whereKv is thevolumeKs thewhichinterfaceanisotropy,andin-planet the thicknessof the magnetic layer.Figure4. Plotof of(a)(a)effectivefunctionofof ttCo(b)KKeffeff Figure4. s 11 andand series 2 as a functiontCotCoCo; ;(b)effeff, ,ofas asa functionofoftCotCo, alongcolour representsrepresentsseriesseries1 1andandbluebluecoloura function, alongwithwiththethestraightstraight lineline fit; red colourcolourrepresentsseries2. 2.representsseries3.2. Effect of Pd ThicknessThe interface anisotropy, which is mainly responsible for the PMA, can be found for a multilayerof particularPd thicknessby plottingthe Keff ontCotheas magnetica functionbehaviorof tCo andcalculatingthe interceptTo understandthe effectof Pd thicknessof Co/Pdmultilayers,two( 2K)fromthecurve[18–22].Figure4bshowstheplotofK twitht.forthetwodifferentotherseries, one with Co layer of thickness 0.2 nm [(Co0.2/PdtPd3)]Coand the other with CosCoeff) 10: (seriesseries.can be seenthatfor[(Coboththe series, Keff 4)],deviatesfrom Theits negative-slopelinear behaviortCowerelayerItthicknessof 0.4nm0.4/Pdt ) 10: (seriesprepared.thicknessof palladium,tPd .Thiseffectcouldbeduetothecoherentused was 0.1, 0.3, 0.6, 0.9, and 1.8 nm. It is to be noted that we have not used Co layer thicker than(uniformstrainin averagethe layer)andincoherentgrowthrespectivelybelowand1 abovecritical0.4 nm, latticesince thisis thelayerthickness(as foundfromthe analysisof seriesand 2),aabovemagneticlayer thickness[23,24].interfaceanisotropy,Ks , calculatedthetheinterceptof the linearwhich Figure 5a,bfromshowsXRD patternsof22fit,theis 0.1170.085seriesandpeakseries2, respectively,whichis comparablefilmserg/cmfor seriesand3 and4. Inerg/cmboth theforcases,no 1suchalong(111) directionis observedfor the tothe values reported for sputtered Co/Pd multilayers [15–18]. The volume anisotropy, Kv , is foundto be 6.78 106 erg/cm3 for series 1 and 3.37 106 erg/cm3 for series 2. The comparatively lowervolume anisotropy of series 2 samples helps the system to favor PMA up to a Co thickness of 0.5 nm.Beyond 0.5 nm, the system prefers in-plane anisotropy. On the other hand, for the series 1 samples,this critical thickness of Co is only 0.3 nm, beyond which the system prefers in-plane anisotropy.3.2. Effect of Pd ThicknessTo understand the effect of Pd thickness on the magnetic behavior of Co/Pd multilayers, twoother series, one with Co layer of thickness 0.2 nm [(Co0.2 /PdtPd ) 10 : (series 3)] and the other with Colayer thickness of 0.4 nm [(Co0.4 /PdtPd ) 10 : (series 4)], were prepared. The thickness of palladium,t Pd , used was 0.1, 0.3, 0.6, 0.9, and 1.8 nm. It is to be noted that we have not used Co layer thickerthan 0.4 nm, since this is the average layer thickness (as found from the analysis of series 1 and 2),above which Co/Pd multilayer system prefers in-plane anisotropy. Figure 5a,b shows the XRD patternsof the films for series 3 and 4. In both the cases, no such peak along (111) direction is observed for the
Sensors 2017, 17, 2743Sensors 2017, 17, 27436 of 126 of 12sampleswitha 0.1nmthickthe rsampleswitha vious, but as sityof(111)peakisobserved.Sensors 2017, 17, 27436 of 12samples with a 0.1 nm thick Pd layer, which is obvious, but as the thickness of individual Pd layerincreases, an enhancement in the intensity of (111) peak is observed.Figure5. (a)seriesFigure5. XRD(θ-2θ)patternscorrespondingsamplesseries3 3andand(b)(b)seriesseries4.4.AAsmallsmallpeakpeak at corresponds to the substrate. 39.5at 39.5 corresponds to the substrate.Figure 5. XRD (θ-2θ) patterns corresponding to samples of (a) series 3 and (b) series 4. A small peakFigures6 correspondsand7 showM-Hcurvesforforthethe seriesseries 33 andand 44 samples,Figures6 and7 thin-planein-planeat 39.5 TheThesaturationsaturation magnetizationmagnetization oTable 2. It can be seen that in both the cases, the 0.1 nm thick Pd layer is not sufficient to give riseand Seriesout-of-planemagneticfield. whenThe saturationmagnetizationvaluesfor these issamplesare monwardsincreased.However,PMA. Series 3 starts to gain PMA when the Pd thickness from 0.3 nm onwards is increased. However,Table2. It canthat in boththe cases,0.1 nm4,thickPd layeris not sufficientto Itgivethisthicknessis benotseensufficientto bringPMAtheto serieswhichhas thickerCo layers.canrisebetoalsothis thickness is not sufficient to bring PMA to series 4, which has thicker Co layers. It can be alsoPMA.3 startsto gainhavePMAdifferentwhen thecoercivityPd thickness0.3 nmPdonwardsis increased.However,seenthatSeriesseries3 samplesforfromdifferentthickness.First, thecoercivityseen thisthatthicknessseries 3 sampleshave ityis notsufficientto bringPMAto series4, differentwhichhasPdthickerCo non-monotoniclayers.It canalsoincreasesand thendecreaseswithPd thickness.This canbe attributedto Thiscanbeattributedtothenon-monotonicchange differentPdthickness.First,thecoercivityof inter-layer ferromagnetic coupling with the increase in spacer layer thickness, as reported earlierinter-layerferromagneticcouplingwiththe increaseincanspacerlayer thickness,as reported changeearlier [25].increasesand thendecreasesPd thickness.be attributedto thenon-monotonic[25].A maximumcoercivityofwith4.3 kOeis found Thisfor thesample(Co0.2/Pd0.6) 10. The squareness of theof inter-layerferromagneticcouplingwith theincreasein spacerlayerthickness,asreportedearlierA ).Thesquarenessof the0.2 field.0.6However, 10M-H curves is also maintained, showing a well-defined switchingin case of series 4[25].A maximumcoercivity ofshowing4.3 kOe isfound for the sample(Co0.2field./Pd0.6)However,ofthe 10. The witchingincaseofseriessamples, the typical squareness is not seen. Rather, the loop becomes narrow as the field is withdrawn 4M-H curvesis alsomaintained,showingwell-definedswitchingfield. However,in fieldcase of4samples,typicalsquarenessis notseen.aRather,loopbecomesas anisotropytheis serieswithdrawnto zero,theindicatingincreased demagnetizingfield theof wasthefieldiswithdrawnto zero,increaseddemagnetizingfieldthese indicatingtwo series ofsamples isshown in Figure8. of the sample. The effective anisotropy energy ofto zero, indicating increased demagnetizing field of the sample. The effective anisotropy energy ofthese two series of samples is shown in Figure 8.these two series of samples is shown in Figure ichysteresisloopssample(a)Figure6.6. 6.In-plane(blacksquare)and plane(black(blacksquare)and sof ofsample(a)loops(Co0.2/Pd0.1) 10, (b) (Co0.2/Pd0.3) 10, (c) (Co0.2/Pd0.6) 10, (d) (Co0.2/Pd0.9) 10, (e) (Co0.2/Pd1.8) 10 of series 3 with(Co0.2/Pd0.1) 10,(b)(Co0.2/Pd0.3) 10,(c)(Co0.2/Pd0.6) 10,(d)(Co0.2/Pd0.9) 10,(e)(Co0.2/Pd1.8) 10ofseries3withof sample (a) (Co0.2 /Pd0.1 ) 10 , (b) (Co0.2 /Pd0.3 ) 10 , (c) (Co0.2 /Pd0.6 ) 10 , (d) (Co0.2 /Pd0.9 ) 10 ,0.2/Pdt ) 10.(Co0.2/Pd(CoPdt )) 10.(e) (CoPd 10 of series 3 with (Co0.2 /Pdt Pd ) 10 .0.2 /Pd1.8
Sensors 2017, 17, 2743Sensors 2017, 17, 27437 of 127 of 12Sensors 2017, 17, 27437 of 127.In-plane(blackandsquare)and out-of-planecircle) hysteresismagnetic loopshysteresisloops (a)FigureFigure7. In-plane(blacksquare)out-of-plane(red circle)(redmagneticof (Co/Pd,0.4 0.3) 100.1, (c) 10 (Co0.4/Pd0.60.4) 10, (d)0.3 10 0.4/Pd0.9)0.4 100.4 series0.9 ) (Co0.4/Pd0.1) 10, (b) (Co0.4/Pd(Co 10, (e)0.6(Co0.4/Pd1.8) 10 of410with(e) (Co/Pd0.4 10(Co0.4/Pd. 1.8 ) 10 of series 4 with (Co0.4 /PdtPd Pd) 10 .tPd Pd)Table 2. Magnetization values of series 3 [(Co0.2 /PdtPd ) 10 ] and series 4 [(Co0.4 /PdtPd ) 10 ] samplescorresponding to different values of t Pd .Serial No.Pd Thickness, tPd (nm)Saturation Magnetizationfor Series 3 (emu/cm3 )Saturation Magnetizationfor Series 4 (emu/cm3 )10.1933112020.3560800Figure 7. In-plane(black square)circle) magnetic hysteresis560loops of sample (a)30.6 and out-of-plane (red350254 0.4/Pd0.9) 10, (e) (Co0.4/Pd1.8431(Co0.4/Pd0.14) 10, (b) (Co0.4/Pd0.30.9) 10, (c) (Co0.4/Pd0.6) 10, (d) (Co) 10 of series 4 with1.8140255(Co0.4/Pd 5Pd) 10.tPdFigure 8. Effective anisotropy, Keff, as a function of tPd for series 3 [(Co0.2/PdtPd ) 10] and series 4[(Co0.4/PdtPd Pd) 10] samples.Table 2. Magnetization values of series 3 [(Co0.2/ PdtPd ) 10] and series 4 [(Co0.4/ PdtPd ) 10] samplescorresponding to different values of tPd .SerialPd Thickness,Saturation Magnetization forSaturation Magnetization forNo.tPd (nm)Series 3 (emu/cm3)Series 4 (emu/cm3)10.1933112020.356080030.6350560Figure 8.8. Effective anisotropy,anisotropy, KKeffeff, as aa functionfunction ofof t PdtPdforforseriesseries3 3[(Co[(Co/PdtPd/Pdand seriesseries 4tPd)) 100.20.210]] and40.9254431/PdPd) 10]samples.[(Co0.4/PdPd)]samples.tt Pd0.4Pd51.8 10140255Table 2. Magnetization values of series 3 [(Co0.2/ Pdt ) 10] and series 4 [(Co0.4/ Pdt ) 10] samplesPdPdIn this case, the compositions with thinner Co layer(series 2) show improvedPMA. Oncorresponding to different values of tPd .comparing the XRD data (Figure 5a,b), it can be seen that the (111) peak corresponding to series 4SerialPd Thickness,Saturation Magnetization forSaturation Magnetization forNo.tPd (nm)Series 3 (emu/cm3)Series 4 (emu/cm3)10.1933112020.3560800
Sensors 2017, 17, 27438 of 12In this case, the compositions with thinner Co layer (series 2) show improved PMA. On comparingSensors 2017, 17, 27438 of 12the XRD data (Figure 5a,b), it can be seen that the (111) peak corresponding to series 4 samples withthickerlayeris morewithenhancedwithpeakenhancedintensity comparedto thatof seriesto3 thatsamplessamplesCowiththickerCoprominent,layer is moreprominent,peak es 3 samples with thinner Co layer of 0.2 nm. Thus, one can expect enhanced PMA in case of seriessincethe (111)provided providedby Pd layerto favor tothePMATheweaker4 samples,sinceorientationthe (111) orientationby isPdconsideredlayer is eries 3 samplesindicatesthat atindicatesthis thicknesslayer(0.2 nm), ofthe CoCo andweaker(111) inreflectionin series3 samplesthat osstheareinterface,and thustheCointerface,atoms gainstrainfilm.(0.2 nm),Co and Pdatomsintermixedacrosstheandlatticethus theCothroughoutatoms gain thelatticeThisin line withtheourfilm.analysisofinseries1 andourseries2 samples,in 1whichwe statedthat belowa CostrainisthroughoutThis isline withanalysisof seriesand series2 samples,in whichthickness 0.3nm ina caseof series 1of(withtPd in0.3nm)0.41nmin casesampleswe statedofthatbelowCo thickness 0.3 nmcaseofandseries(withtPd of0.3seriesnm) 2and0.4 nm(withintcase owthortheCo-PdalloyformationPd of series 2 samples (with tPd 0.9 nm), coherent growth takes place. Thus, the coherent growth isthecauseof enhancedPMA in3 samples.or theCo-Pdalloy formationis seriesthe causeof enhanced PMA in series 3 samples.3.3.3.3. TEMTEM CharacterizationCharacterizationTEM) , 10which, whichshowedthemaximummaximumPMA,PMA,waswasTEM characterizationcharacterization ofof thethe samplesample (Co(Co0.20.2/Pd/Pd0.60.6) gcross-sectionalTEMTEMspecimen,a 2-micronperformed usingusinga pecimen,a 2thickplatinumlayer wasdepositedaboveabovethe multilayer,and theof thesamplewasmicronthick platinumlayerwas depositedthe multilayer,andcross-sectionthe cross-sectionof thesampleobtainedby cuttingthe sampleusing focusedion beamtechnique(FIB), as discussedin supportingwas obtainedby cuttingthe sampleusing focusedionbeam technique(FIB), as discussedininformationof Referenceof[26].The cross-sectionalTEM images TEMof theimagessampleofwereat ansupporting informationReference.[26]. The cross-sectionalthe obtainedsample wereaccelerationvoltageof 200voltagekV. Figure9akV.showsa high-resolutioncross-sectio
For structural characterization of the films, we performed XRD studies using a Bruker D2 Phaser X-ray Diffractometer with Cu-Ka radiation. A high-resolution JEOL 2800S/TEM system was. Sensors 2017, 17,
anisotropy and calcite strains in Devonian carbonates from the Appalachian Plateau, New York. Tectonophysrcs. 161: 43-53. Anisotropy of anhysteretic susceptibility (AAS) is a recently developed high-resolution method of measuring the magnetic fabric of rocks. In order to test the applicability and limitations of AAS for estimation of strain .
A) Rotating perpendicular lines result in parallel lines. B) The lines remain perpendicular only if rotated 180 . C) The lines remain perpendicular only if rotated 360 . D) Rotated perpendicular lines always remain perpendicular lines. Explanation: Rotated perpendicular lines always remain
Magnetic stir bar, Ø 3x6 mm A00001062 Magnetic stir bar, Ø 4.5x12 mm A00001063 Magnetic stir bar, Ø 6x20 mm A00001057 Magnetic stir bar, Ø 6x35 mm A00001056 Magnetic stir bar, Ø 8x40 mm A00000356 Magnetic stir bar, Ø 10x60 mm A00001061 Magnetic cross shape stir bar, Ø 10x5 mm A00000336 Magnetic cross shape stir bar, Ø 20x8 mm A00000352
In a plane, if a transversal is perpendicular to one of two parallel lines, then it is perpendicular to the other line. If h k and j h, then j k. Proof Example 2, p. 150; Question 2, p. 150 Theorem 3.12 Lines Perpendicular to a Transversal Theorem In a plane, if two lines are perpendicular to the same line, then they are parallel to .
a. Parallel to . b. Perpendicular to . c. Parallel to . d. Perpendicular to . 2. Write the equation of the line through @ A and: a. Parallel to . b. Perpendicular to . c. Parallel to . d. Perpendicular to . 3. A vacuum robot is in a room and charging at position . Once charged, it begins moving on a northeast path at
Any two vertical lines are parallel. Postulate 18 Slopes of Perpendicular Lines In a coordinate plane, two nonvertical lines are perpendicular if and only if the product of their slopes is -1. The slopes of the two lines that are perpendicular are negative reciprocals of each other. Horizontal lines are perpendicular to vertical lines
Experimental Analysis of Acoustic Anisotropy of Green Wood by using Guided Waves . of stress waves and the natural anisotropy axis in the cross section. Wave velocities are measured on Douglas .
The effects of strength anisotropy of geomaterials in slope stability problems are the focus of this paper. The source of the strength anisotropy could be attributed to many factors and the motivation of this study is to concentrate on the effects of plane of weaknesses, such as joints, bedding planes etc. on the slope stability analysis.
