Direction Of Magnetic Anisotropy Research Articles

Magnetic properties and domain structures of FeNiMo/FeCoV double-layer films

The presence of an FeNiMo underlayer (a few tens Å thick) with magnetic anisotropy between an FeCoV (a few thousands Å thick) and the substrate is found to change the magnetization process and reduce the coercive force of the FeCoV magnetic layer to about 3–10% of the original value with little reduction in saturation magnetization. This suppression of coercive force of the FeCoV layer does not occur when the FeNiMo is not present between the FeCoV layer and the substrate. The exact nature of the change in magnetic behavior of the FeCoV layer as well as the degree of reduction is found to be dependent on the existence and direction of magnetic anisotropy in the FeCoV magnetic layer upon deposition. The insertion of a non-magnetic Cu layer (100 Å thick) between the magnetic layers does not retard these effects, whereas the insertion of Si in a similar manner completely eliminates these effects. The results suggest that magnetic interaction between the magnetic anisotropy of these layers is responsible for these effects.

Kerr microscopy study on sputtered fe stripes

Sputtered polycrystalline iron gratings with a varying stripe width between 0.5 and 3.7 /spl mu/m at a constant periodicity of 5 /spl mu/m were studied by Kerr microscopy. The magnetic anisotropy direction is aligned transverse to the stripe length axis. The observed domain processes are directly compared with hysteresis curve measurements. Domain nucleation and the resulting domain structure depend on the external magnetic field direction. Complicated multidomain states are observed down to a stripe width of 1.7 /spl mu/m. The most narrowly spaced stripes display a simple domain configuration with the average magnetization vector perpendicular to the stripes, along the full film anisotropy axis, indicating dipolar coupling between the elements. With decreasing stripe width and increasing stripe distance, a change to a Landau-Lifshitz-like domain pattern is found. For very narrow stripes, it transforms into a ripple modulated domain structure. Altogether, a continuous transition from full-film-like to single strip-like magnetization behavior with increasing stripe spacing is found. The results are explained by the existing uniaxial magnetic anisotropy together with the shape anisotropy increasing with reduced stripe width. The strong influence of coercivity on the magnetization patterns is shown.

Temperature dependence of magnetization reversal in TbFeCo films

The magnetization reversal process has been studied in a series of four TbFeCo films over the temperature range 300–460 K. The films were characterized by time decay, dynamic coercivity, Kerr imaging, and torque measurements. For a film with a sputter-etched SiN underlayer, the reversal process at low temperatures was dominated by nucleation followed by rapid domain wall motion. The low temperature relaxation curves for this sample were analyzed using a Fatuzzo model. At high temperatures, the Fatuzzo model did not apply. For the other films, with no etching, relaxation curves were logarithmic at all temperatures. All activation volumes increased with increasing temperature and decreased with increasing sputtering pressure. The magnetic anisotropy direction changed from perpendicular to in-plane as the argon sputtering pressure was increased.

Rf 마그네트론 스퍼터링으로 제조된 퍼멀로이 박막의 자기이방성 조절을 위한 NdFeB 영구자석의 영향 및 자기특성 해석

Permalloy thin films fabricated by rf magnetron sputtering showed the excellent magnetic properties, i.e., an effective permeability of over 2000 at 1 thick up to 10 MHz, a saturation magnetization of 10∼12 kG, a coercive force of 0.2∼1 Oe, resistivity (p) is 20 cm. In order to control the magnetic anisotropy direction of the films in a wafer scale, two parallel Nd-Fe-B permenant mangnets were used to provide the magnetic field during the sputtering process. As a result, the anisotropy direction was successfully controlled when the two magnets were seperated with a distance of 70 mm. 3D simmulation of the magnteic fields around the wafer during sputtering were in accord with the above result.

The effect of anisotropy in Co/sub 66/Fe/sub 4/Ni/sub 1/B/sub 14/Si/sub 15/ ribbon on the transverse incremental permeability and magnetoimpedance

The transverse incremental permeability and magneto-impedance effects in amorphous Co/sub 66/Fe/sub 4/Ni/sub 1/B/sub 14/Si/sub 15/ ribbons treated with various annealing and etching conditions have been investigated in conjunction with their magnetic anisotropy. The shape and the depth of double peaks in magneto-impedance ratio (MIR) and transverse permeability ratio (TPR) curves show the existence of the uniaxial magnetic anisotropy. The direction of magnetic anisotropy in samples annealed under magnetic field was induced parallel to their magnetic field. The direction of magnetic anisotropy in samples annealed without the magnetic field has changed ribbon to width direction. The surface etching of an as-quenched sample helps to orient the magnetic anisotropy to the ribbon axis. The maximum values of MIR and TPR depend on the magnetic softness rather than the direction of magnetic anisotropy. However, the shapes of MIR and TPR curves strongly depend on their uniaxial magnetic anisotropy.

Giant magnetoimpedance in twisted amorphous CoP multilayers electrodeposited onto Cu wires

CoP multilayers grown over Cu wires exhibit magnetoimpedance phenomenon. The change in the real part of the measured voltage is V R = [ V( H = 0 Oe)- V( H max)]/ V( H max) ≈ 3300%( I rms = 500 mA, 90 kHz); the maximum d V R/d H, is 1280%/Oe at H DC = 1.2 Oe. These quantities are enhanced if the wire is subjected to an angular deformation by means of a torque applied to the wire; V R ≈ 7000% and d V R/d H ≈ 2400%/Oe, are found at 9 and 1.2 Oe, respectively, for a 90° twisted sample, produced by the change in the magnetic anisotropy direction, from the longitudinal to the helical one.

The use of stress for the control of magnetic anisotropy in amorphous FeSiBC thin films: a magneto-optic study

Magnetostrictive FeSiBC amorphous thin films based on the METGLAS ® 2605SC composition have been produced by RF magnetron sputtering. The magnetic properties were investigated using the magneto-optical Kerr effect, with both point hysteresis measurements and domain imaging. Significant in-plane anisotropy is observed in the as-grown samples, which was attributed to the residual field from the magnetron sputter source. The effects of various treatments on the samples were investigated, including the use of forming fields, stress, and thermal processing. The deliberate introduction of stress into these materials is found to allow excellent control of both the direction and magnitude of magnetic anisotropy, and can also be used as a novel method for the absolute measurement of magnetostriction. The treatments are evaluated for their potential to control anisotropy in magnetostrictive device applications.

Effect of atomic short-range order on magnetic anisotropy

Abstract We present a theory to study the relation between compositional order and magnetocrystalline anisotropy of ferromagnetic alloys. The ordering phenomenon is represented by static concentration waves. The electronic part is described within the spin-polarized relativistic Korringa-Kohn-Rostoker coherent-potential approximation. This scheme can be used to investigate the change in the magnitude as well as the direction of magnetic anisotropy in an alloy at the onset of ordering. The same framework can also be used to study directional chemical order produced by magnetic annealing. We have calculated the magnetocrystalline anisotropy energy of ordered fcc-Co0.5Pt0.5 alloy using this method. We find that the magnetocrystalline anisotropy energy of the ordered phase is two orders of magnitude larger than that of the disordered phase. Also, that the direction of ‘easy’ magnetization in the ordered phase depends on the type of ordering. These results are in good agreement with the experimental observations.

Control of crystallographic and magnetic texture in dc-magnetron sputtered Co–Cr on flexible PET substrate

The paper reports on hard-magnetic thin films on flexible PET substrates. The total coating stack is deposited in a roll-coater by dc-magnetron sputtering and includes a Cr underlayer, a Co–Cr magnetic layer, and an SiO 2 wear-resistant layer on top. The influence of various deposition parameters on crystallographic and magnetic properties has been investigated. The magnetic anisotropy direction in Co–Cr can be changed from perpendicular to in-plane by applying a (very thin) Cr underlayer. This in-plane anisotropy is directed in the machine direction, probably due to an anisotropic magnetostriction. No clear relation between coercivity and crystallinity or grain size is observed. The coercivity is mainly influenced by film thickness and substrate temperature. For Co–Cr without Cr underlayer, an increasing temperature results in increased coercivity and more distinct grains. For Co–Cr with Cr underlayer, an increasing temperature results in decreased coercivity and less distinct grains.

CoP electrodeposited multilayer with varying magnetic anisotropy direction

Abstract Over a 60 μm film with perpendicular anisotropy, a composition modulated multilayer, of the same material, has been grown. Investigations using Bitter domain configuration observations and surface hystetic loop measurements using magneto-optic Kerr rotation show that the multilayer magnetization process is coupled with the underlayer anisotropy for multilayer thickness of the order of the bulk stripes domain width.

Calculation of spin-reorientation temperature in Nd2Fe14B

The spin-reorientation phenomenon in Nd2Fe14B has been investigated using an angular dependent free energy approach. A magnetic Hamiltonian which includes the crystal electric field term and the exchange term has been established using realistic band structure results. The temperature dependence of the molecular field is accounted for by introducing the Brillouin function and the magnetic Hamiltonian is diagonalized within the ground state multiplet of the Nd ion. The eigenstates are then used to form the partition function for the free energy. At each temperature, the direction of the molecular field is obtained by searching for the minimum in the angular parameter space of the free energy. Our calculations show that for Nd2Fe14B, the net magnetic anisotropy direction is canted away from the c axis at a temperature close to the experimentally reported spin-reorientation temperature of 150 K. The temperature dependence of the magnetic structure is found to be very sensitive to the size of the second order crystal field parameter B20.

Magnetic and thermomagnetic analysis of metal evaporated tape

Metal evaporated (ME) tape is being developed as an advanced medium for high-density magnetic tape recording. It is produced by evaporation in an oxygen atmosphere, and consists of very small Co and CoNi crystallites intermingled with oxides of Co and Ni. The angle of incidence of the vapor flux is varied continuously during deposition, imparting to the film a distinct curved columnar structure. Previous studies have measured the angular dependence of the coercivity and remanence out of the plane of the tape in order to determine the preferred direction of magnetic anisotropy and the mechanism of magnetization reversal in these films. These studies, however, do not take into account the demagnetizing field. In this study, we used a two-dimensional vector vibrating-sample magnetometer (VSM) to obtain the correct angular dependence of the coercivity and of the remanent magnetization. Our results show that magnetization reversal near the easy axis proceeds by incoherent rotation, and not by domain-wall displacement as suggested by other investigators. We also measured the torque characteristics in the three principal planes and used them to determine the magnitude and angle of the uniaxial magnetic anisotropy in these films. To understand the origin of the magnetic anisotropy, we studied the temperature dependence of Ms and Hc over the range of −100 to +100 °C. We found that Ms is essentially independent of temperature in this range, while Hc has a very large negative temperature coefficient (about 6 Oe/°C). This implies that it is primarily the crystalline anisotropy of the Co and CoNi crystallites which controls the coercivity of these films, and not the shape of the distinct columnar structure or any shape contribution of the crystallites themselves.

Phase diagram of magnetic and structure transformations in MnAs 1- xP x

From the measurement data on static crystal lattice distortion determining magnetic anisotropy and magnetic moment direction, it is shown that below T t = 400−450 K in the MnAs 1- x P x ( x ⩽ 0,1) alloys a disordered modulated magnetic structure is formed. The boundaries of the unstable crystal structure with atomic coordinates variable are refined.

The effect of evaporation conditions on selected properties of thin amorphous Gd-Fe films

Changes in the thickness and chemical composition of thin amorphous Gd-Fe films were studied as a function of the substrate-source distance and as a function of the active surface area of the heater. The evaporation time interval leading to the maximum uniformity of the films obtained was also determined.For selected samples the hysteresis loop was measured from VH=f(H) using the transverse Hall effect. Some films exhibited rectangular hysteresis loops suggesting the existence of a magnetic anisotropy direction perpendicular to the surface of the deposited layer.

Magnetization, magnetic anisotropy, and domain patterns of Fe80B20 glass

The thermomagnetization behavior, magnetic anisotropy, and magnetic domain patterns of ribbons of the newly synthesized Fe80B20 glass have been examined. This glass exhibits a saturation moment of 1.99 μB/Fe atom, a ferromagnetic Curie temperature of 647 K, and a crystallization temperature of ∼660 K. The direction of magnetic anisotropy lies at ∼60° to the ribbon axis in the plane of the ribbon. Large domains, elongated parallel to the ribbon axis, are observed.

冷間圧延したVicalloy磁石の磁気異方性の圧延率に対する依存性

Vicalloy specimens composed of 2∼3%Cr, 9∼8%V, 52%Co, balance Fe were reduced in thickness from 33% to 93% by cold-rolling and then subjected to tempering at temperatures between 100° and 750°C. The severer is the cold reduction, the higher become the saturation magnetization and uniaxial roll magnetic anisotropy.The easy direction of uniaxial roll magnetic anisotropy in rolled state is perpendicular to the rolling direction. After tempering at about 400°C, the uniaxial magnetic anisotropy disappers, a slight cubic magnetic anisotropy remaining only. After tempering at about 600°C, the uniaxial magnetic anisotropy appears again, but its easy direction becomes parallel to the rolling direction. When the cold-rolled alloys are tempered at 500°∼600°C, the coercive force and mechanical hardness increase, but the saturation induction decreases. In this case, the severer is the degree of cold reduction, the harder is the mechanical hardness, but the lower is the coercive force. An increase of the coercive force is due to the partial transformation of the alpha phase to the gamma phase, during which finely dispersed particles of the gamma phase are formed.The saturation magnetization and coercive force as a function of the temperature from −70° to +530°C are measured. The saturation magnetization of specimens reduced slightly in thickness increases rapidly below +80°C and the highest value of coercive force is obtained at about +80°C. However, in the case of severe reduction, the curves of the saturation magnetization and of coercive force as a function of the temperature do not reveal the above-mentioned changes.

Anisotropy Rotation in Thin Permalloy Films at Room Temperature

It has been observed that the magnetic anisotropy direction of certain thin Permalloy films prepared by the thermal decomposition of nickel and iron carbonyls can be rotated through 90 deg at room temperature by fields less than 10 oe. The experimental conditions under which these films were prepared suggest that this phenomenon is due to the presence of carbon. The relaxation time for the rotation of the anisotropy axis was calculated from the time dependence of the induction and found to be 10 msec. A simple model has been developed which relates the anisotropy rotation to specific domain wall configurations and to the establishment of a “directional order” among interstitial carbon atoms.