Thickness Dependence Of Magnetic Properties Research Articles

Thickness dependence of magnetic properties of Ir/FeV-based systems

Ir-buffered ${\mathrm{Fe}}_{0.7}{\mathrm{V}}_{0.3}$ (FeV) thin films of variable thickness ($1.4\phantom{\rule{0.28em}{0ex}}\mathrm{nm}\ensuremath{\le}{t}_{\mathrm{FeV}}\ensuremath{\le}10\phantom{\rule{0.28em}{0ex}}\mathrm{nm}$) were sputtered on thermally oxidized Si substrate and capped with Cu or MgO films. Vibrating sample magnetometery measurements allowed deducing their magnetization at saturation and the magnetic dead layer thickness, found to be capping layer independent. Microstrip line ferromagnetic resonance measurements under in-plane and perpendicular to the film plane applied magnetic fields are employed to investigate the perpendicular magnetic anisotropy (PMA) and damping. PMA is found to result from a uniaxial interfacial contribution which is slightly capping layer dependent. In contrast, the second-order PMA constant, which could result from the inhomogeneous distribution and the spatial fluctuations at the nanoscale of the uniaxial PMA at interface, is significantly stronger for Ir/FeV/Cu films. The damping dependence on the inverse of FeV effective thickness revealed a low Gilbert damping constant for FeV $({\ensuremath{\alpha}}_{\mathrm{FeV}}=1.7\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3})$ and allowed concluding that damping enhancement is mainly induced by Ir/FeV. The zero frequency linewidth for in-plane configuration is attributed to two magnon scattering contribution, found to be higher for Cu capped FeV. The investigation of the FeV thickness dependence of interfacial Dzyaloshinskii-Moriya interaction (iDMI) of both systems via Brillouin light scattering allowed to conclude to the zero iDMI constant of FeV/Cu. It also led to deduce iDMI constants of Ir/FeV and FeV/MgO, estimated to be ${D}_{\mathrm{s}}^{\mathrm{Ir}/\mathrm{FeV}}=(0.13\ifmmode\pm\else\textpm\fi{}0.02)\phantom{\rule{0.28em}{0ex}}\mathrm{pJ}/\mathrm{m}$ et ${D}_{s}^{\mathrm{FeV}/\mathrm{MgO}}=(\ensuremath{-}0.07\ifmmode\pm\else\textpm\fi{}0.02)\phantom{\rule{0.28em}{0ex}}\mathrm{pJ}/\mathrm{m}$, respectively.

Thickness Dependence of Magnetic Properties of Tb–Co/Ti and Tb–Co/Si Multilayers

Nanoscale [Tb–Co/Ti]n and [Tb–Co/Si]n multilayers were designed and prepared by the rf-sputtering technique. Their structure and magnetic properties have been experimentally studied. Low-angle X‑ray diffraction studies confirmed that a well-defined layered structure was formed in all investigated cases. The change in the magnetic properties of multilayers with a decrease in the thickness of the Tb–Co layers was due to both the size effect and the influence of the material of the non-magnetic spacers, namely the reduction of the Co atom moment because of the electron charge transfer from atoms of the Ti or Si spacers to atoms of the cobalt.

Tuning ferromagnetic properties of LaMnO3 films by oxygen vacancies and strain

Abstract We systematically investigated the ferromagnetic properties of LaMnO3 (LMO) films grown on SrTiO3 (STO) substrates with varying deposition oxygen pressure PO2 (0.2 ≤ PO2 ≤ 200 mTorr). It was found that the films only deposited with PO2 ≤ 20 mTorr showed exchange bias behavior and meantime the coercive field HC of LMO films deposited below 20 mTorr is about one order of magnitude larger than that of films deposited at 200 mTorr. When the LMO films were deposited at 20 mTorr on different substrates [LaAlO3 (LAO), (LaAlO3)0.3(Sr2AlTaO6)0.7 (LAST), SrTiO3 (STO) and KTaO3], LMO/STO sample showed the maximum HC, even though all of them exhibit exchange bias behavior. Thickness dependence of magnetic properties in LMO/STO films deposited at 20 mTorr indicated a maximum coercive field and the existence of exchange bias for 20 nm-thick LMO sample. Based on our results, the enhancement of coercive field and exchange bias was attributed to the competition between different magnetic phases induced by oxygen vacancies and Jahn-Teller effect from strain-induced orbital ordering.

Thickness dependence of magnetic properties in submicron yttrium iron garnet films

Yttrium iron garnet (YIG) films with various thicknesses have been fabricated by liquid-phase epitaxy (LPE) on gadolinium gallium garnet (GGG) (1 1 1) substrates showing unusual magnetic properties. In this work, we studied YIG films with thicknesses between 100 nm and 1000 nm and compared them with La3+-doped YIG films (La:YIG) over a similar scale. The relaxation of tensile stress at the GGG/YIG interface, which caused a magnetic hysteresis loop, showed an easy magnetization phase for thin YIG films (⩽400 nm), while a hard magnetization phase gradually appeared with further increases to the film thickness. The stable magnetic properties of La:YIG at different thicknesses and the not so perfect magnetic hysteresis loop are caused by the intrinsic distortion of the sublattice from La3+ partially replacing Y3+. The saturation magnetization field (4πMs) obtained from broadband ferromagnetic resonance measurement of the YIG films increased with increasing Ha and stayed around the theoretical value. This work helps us to understand the properties of LPE-based YIG films and devices at the sub-microscale.

Thickness dependence of magnetic properties of thin amorphous ferrimagnetic rare earth–transition metal multilayers

Gd-Co/Ti multilayers were prepared by magnetron sputtering deposition onto glass substrates. The temperature dependence of magnetization of the multilayered structures depends on the Gd-Co layer thickness. It was shown that the obtained experimental results can be satisfactorily described in the framework of the joint application of models of the “size factor” and the “molecular field”. In addition, the possible effect of the electronic structure of titanium on the average magnetic moment of Co atoms, the efficiency of which depends on the thickness of the magnetic layers was also taken into account.

Random Magnetic Anisotropy Studies in SmCo5 Thin Films

SmCo5 thin films with different thicknesses were prepared by electron beam evaporation on Kapton substrates. The out-of-plane hysteresis loops for different thicknesses reveal a maximum coercive field when the thickness is 15 nm. Using random magnetic anisotropy model, the thickness dependence of magnetic properties was studied in SmCo5 nanocrystalline films and several fundamental magnetic parameters were extracted. We have determined the local magnetic anisotropy constant K 1 which is found to increase with increasing film thickness except for t = 7 nm which is thought to arise from the structural imperfection of the SmCo5 films.

Thickness dependence of magnetic properties and giant magneto-impedance effect in amorphous Co73Si12B15 thin films prepared by Dual-Ion beam assisted deposition

Dual-Ion Beam Assisted Deposition is a suitable method for the preparation of giant magneto-impedance (GMI) materials. In this paper, Co73Si12B15 thin films with different thicknesses were prepared by Dual-Ion Beam Assisted Deposition, and the influences of film thickness on magnetic properties and GMI effect were investigated. It was found that the asymmetric magnetic hysteresis loop in the prepared Co73Si12B15 thin films occurs at ambient temperature, and the shift behavior of hysteresis loop associated with film thickness. With the film thickness increasing, the values of shift field and coercive field and other parameters such as remanence and shift ratio appeared complex variation. At a certain frequency, the large GMI effect is only observed in some films, which have good magnetic properties including low coercivity, low remanence ratio and high shift ratio. The results indicated that the thickness dependence of magnetic properties nonlinearly determined the GMI effect in Co73Si12B15 thin films.

Ferrimagnetic Tb–Fe Alloy Thin Films: Composition and Thickness Dependence of Magnetic Properties and All-Optical Switching

Ferrimagnetic rare earth - transition metal Tb-Fe alloy thin films exhibit a variety of different magnetic properties, which depends strongly on composition and temperature. In this study, first the influence of the film thickness (5 - 85 nm) on the sample magnetic properties was investigated in a wide composition range between 15 at.% and 38 at.% of Tb. From our results, we find that the compensation point, remanent magnetization, and magnetic anisotropy of the Tb-Fe films depend not only on the composition but also on the thickness of the magnetic film up to a critical thickness of about 20-30 nm. Beyond this critical thickness, only slight changes in magnetic properties are observed. This behavior can be attributed to a growth-induced modification of the microstructure of the amorphous films, which affects the short range order. As a result, a more collinear alignment of the distributed magnetic moments of Tb along the out-of-plane direction with film thickness is obtained. This increasing contribution of the Tb sublattice magnetization to the total sample magnetization is equivalent to a sample becoming richer in Tb and can be referred to as an “effective” composition. Furthermore, the possibility of all-optical switching, where the magnetization orientation of Tb-Fe can be reversed solely by circularly polarized laser pulses, was analyzed for a broad range of compositions and film thicknesses and correlated to the underlying magnetic properties.

Thickness dependence of magnetic properties in La–Co substituted strontium hexaferrite films with perpendicular anisotropy

The thickness dependence of magnetization reversal and coercivity behavior for La–Co substituted strontium hexaferrite (Sr-M) films was investigated. It is found that perpendicular anisotropy appears only when film thickness (t) is above 110nm. With increasing t, perpendicular anisotropy energy (Ku⊥) increases gradually to its maximum of 1.76×106erg/cm3 at t=300nm, but turns to decrease when t>300nm. Moreover, when t>110nm, those films exhibit domains pinning or Stoner–Wohlfarth reversal model, present large Ku⊥ values and a rapid increase in Hc⊥. However, while t≤110nm, Sr-M films show nucleation model of magnetization reversal and perform low coercivity. The origin of the coercivity varying with thickness should be correlated with the grain size and preferred orientations in Sr-M films.

Annealing temperature and thickness dependence of magnetic properties in epitaxial L1-Mn1.4Ga films

Mn1.4Ga films with high perpendicular magnetic anisotropy and high crystalline quality were grown on MgO substrates with Cr buffer layer using molecular beam epitaxy. The crystalline structure and the surface morphology of the films have been systematically investigated as functions of in-situ annealing temperature (Ta) and film thickness. It is found that the magnetic properties can be largely tuned by adjusting Ta. As Ta increases, both saturation magnetization (Ms) and uniaxial perpendicular magnetic anisotropy constant (Ku) increase to the maximum values of 612 emu/cc and 18 Merg/cc at 300 °C, respectively, and then decrease. The morphology also changes with Ta, showing a minimum roughness of 2.2 Å at Ta = 450 °C. On the other hand, as the thickness increases, Ms and Ku increase while coercivity decreases, which indicates there is a magnetic dead layer with a thickness of about 1.5 nm at the interfaces. The detailed examination on the surface morphology of the films with various thicknesses shows a complicated film growth process, which can be understood from the relaxation mechanism of the interfacial strain.

Tailoring magnetism at the nanometer scale in SmCo5 amorphous films

The thickness dependence of magnetic properties has been studied in SmCo5 amorphous films with imprinted in-plane anisotropy for thicknesses ranging down to the nanometer scale (2.5–100 nm). The field induced in-plane magnetic anisotropy decreases considerably when the film thickness is below 20 nm. Analysis of the magnetic anisotropy energy shows that the decrease of the induced in-plane anisotropy is accompanied by the development of an out-of-plane interface anisotropy. Two different regimes for the coercivity (Hc) change are found: below 3.75 nm, the Hc decreases continuously with decrease of the film thickness, whereas at above 3.75 nm, the Hc decreases with increase of the film thickness. This change in Hc can be understood by considering the decrease of the short range chemical order for the thinnest films (<3.75 nm) and the relative decrease of the interface contribution with increasing film thickness. The changes in anisotropy have a profound influence on the domain structure, in which the angle of the zigzag domain boundaries decreases with the inverse thickness of the layers.

Fe-Hf-N 연자성 박막의 자기적 특성에 미치는 박막 두께의 영향

The thickness dependence of magnetic properties was experimentally investigated in nanocrystalline Fe-Hf-N thin films fabricated by a RF magnetron sputtering method. In order to investigate the thickness effect on their magnetic properties, the films are prepared with different thickness ranges from 90 nm to 330 nm. It was revealed that the coercivity of the thin film increased with film thickness. On the contrary, the saturation magnetization decreased with film thickness. On the basis of the SEM and TEM, an amorphous phase forms during initial growth stage and it changes to crystalline structure after heat treatment at <TEX>$550^{\circ}C$</TEX>. Nanocrystalline Fe-Hf-N particles are also generated.

Magnetic and Transport Properties of Mn-Si Films Synthesized on 4H-SiC(0001) Substrates

We report a systematic study of the thickness dependence of magnetic properties in carbon-incorporated Mn-Si films synthesized on a 4H-SiC(0001) homoepitaxial wafer by molecular beam epitaxy (MBE) and an annealing method. Magnetization characteristics reveal a dual-phase characteristic in films with decreasing thickness. The anomalous Hall effect has been observed in the thicker film; however, the observed temperature dependence cannot be explained by traditional anomalous Hall effect theory. The temperature dependent resisitivity indicates the film has a metallic behavior.

Local magnetic effects of interface alloying in Fe/Co superlattices

Effects of interface alloying and the thickness dependence of magnetic properties ofFe/Co(001) multilayers have been investigated. The thicknesses of the Fe layers have beenvaried between two and 14 monolayers while the Co layers have been held constant at 7 ML.From conversion electron Mössbauer spectroscopy (CEMS) measurements andelectronic structure calculations it is found that the magnitude of the Fe magnetichyperfine field is larger close to the interface and smaller in the middle of thick(≥9 ML) Fe layers. Fora thinner Fe layer (≤5 ML) the largest field is found in the centre of the Fe layer. By modelling the effects ofinterface alloying from earlier data for bulk Fe–Co alloys, and comparing with theexperimental results, the degree of interface alloying is estimated to be 2–3 ML at eachinterface.

On the range of interaction from finite size scaling in magnetic Ni nanowires

A recent experiment reporting a thickness dependence of magnetic properties of Ni nanowires has been re-interpreted in terms of spin–spin interactions eventually ranging beyond nearest neighbors. An analysis following the Ginzburg argument indicated that the system is in the crossover regime from 3D Ising to classical critical behavior as a function of the normalized range of interactions R . The range of the interactions covering three to four coordination spheres of an Ni atom has been found by the fit to literature experimental data on Ni nanowires. Consistency with recent first-principles calculations are discussed.

Magnetic anisotropy and its thickness dependence for NiFe alloy films electrodeposited on polycrystalline Cu substrates

The thickness dependence of magnetic properties of NiFe alloys electrodeposited on polycrystalline copper substrates has been investigated. In order to see how the film thickness affects their properties, the films with various thicknesses were deposited by keeping the cathode potential at −1.5 V vs. the saturated calomel reference electrode (SCE). Magnetic measurements show that the magnetic properties are very sensitive to the film thicknesses and, the easy axis of all films is in the film plane. The results showed that the 1 and 2 μ m thick NiFe films are anisotropic and the degree of their anisotropy depends on film thickness whereas those deposited at the thickness of 3 μ m show an isotropic magnetic behaviour. It is also found that the increase of the nickel content when increasing their thickness results in an increase in the coercivity values.

Thickness effect on magnetic properties of nanocrystalline CoFeBN soft magnetic thin films

The thickness dependence of magnetic properties was examined in nanocrystalline CoFeBN films fabricated by a RF magnetron sputtering method. It was revealed that the coercivity of the films abruptly increased at a critical thickness without any noticeable microstructural difference. In addition, high B, N contents decreased the critical thickness. These behaviors were discussed in connection with residual film stress.

Thickness dependence of magnetic properties in DyFeCo films

Films of amorphous DyFeCo were deposited on glass substrates using RF sputtering deposition system. The thickness dependence of the coercivity of DyFeCo films prepared under the same sputtering conditions was investigated. It is found that the composition is nearly thickness independent, while the coercivity is shown to increase with the film thickness increasing at the beginning, then above a certain thickness decrease with the thickness increasing. The thickness dependence of the coercivity is believed to be due to microstructure-induced variations in the short-range order during the film growth.

Thickness dependence of incremental permeability in Mumetal( t)/CoCr bilayers

The thickness dependence of magnetic properties in mumetal( t)/CoCr(500 nm) bilayers for t=700, 1400, and 2100 nm was studied by measuring incremental permeability. In order to induce in-plane magnetic anisotropy, the deposition was performed in a DC magnetic field of 300 Oe parallel to the film plane and the directions of anisotropy in pinned layer were parallel to those in soft layers. Transverse permeability ratio curves showed the symmetric single peak at zero magnetic field and the values were increased with increase in thickness. Longitudinal permeability ratio curves also showed that the single peak and the peak positions were shifted from zero magnetic field, and reduced with the decrease of bias fields generated by CoCr layer. The asymmetric permeability ratio curves are considered as the effect of exchange coupling between the soft magnetic mumetal layer and the pinning CoCr layer.

Preparation and thickness dependence of magnetic properties of (1 1 1)-oriented Mg 1.5FeTi 0.5O 4 spinel films on sapphire by pulsed laser deposition technique

Thin films of (1 1 1)-oriented Mg 1.5FeTi 0.5O 4 spinel have been successfully prepared by a pulsed laser deposition (PLD) technique on α-Al 2O 3 (0 0 0 1) substrates. The value of the lattice parameter of the (1 1 1) out-of-plane and the Néel temperature of the films depend on the film thickness. The spin-glass behavior has been observed with a freezing temperature of 100 K, which is 80 K higher than that of the bulk material. This freezing temperature is reduced by increasing the oxygen pressure during film preparation. These results show that the PLD technique is promising not only for obtaining thin films of oxide materials under a wide range of conditions but also for controlling the magnetic properties of films.