Toshikazu Katayama

Wavelength Dependence of Magneto-Optical Kerr Rotation in Co/Cu, Fe/Cu, Co/Au and Fe/Au Compositionally Modulated Multilayered Films

The wavelength dependence of polar magneto-optical Kerr rotation angle (θ K ) was measured in compositionally modulated multilayered films (CMF) composed of Co/Cu, Fe/Cu, Co/Au and Fe/Au systems. The value of θ K is low and the shape of wavelength dependence is relatively flat in the CMF with modulation length less than nearly 20A. However, a new θ K peak appears at around λ=560 nm in Co/Cu and Fe/Cu CMF and around λ=500 nm in Co/Au and Fe/Au CMF with large modulation length. These wavelengths correspond to the absorption edge of Cu and Au metals, respectively.

Oscillation of saturation magneto-optical Kerr rotation in epitaxial Fe/Au/Fe and Fe/Ag/Fe(100) sandwiched films

Abstract We report on the behavior of saturation polar Kerr rotation (φK) spectra and their oscillation due to interlayer thickness in Fe/Au/Fe and Fe/Ag/Fe sandwich films. An oscillation of φK as a function of d was observed in the photon energy region between about 2.5 and 3.8 eV for Fe(6 A)/Au(d A)/Fe(6 A) sandwiched films. The oscillation period was about 5ML (10 A) of Au. Similar results were also observed in Fe/Ag/Fe films. The oscillation is thought to be closely related with the formation of spin polarized quantum well states of the Δ1 band in Au layers sandwiched by magnetic layers.

Fabrication and magneto-optical properties of epitaxial ferromagnetic Mn1 − xSb thin films grown on GaAs and sapphire

Abstract We succeeded in growing epitaxial ferromagnetic Mn 1 − xSb thin films by molecular beam epitaxy (MBE). The crystal structures were of NiAs-type and their orientations changed depending on the substrate, (10.1) for (001) GaAs and (00.1) for (00.1) sapphire. The sharp X-ray diffraction patterns showed that these epitaxially grown films were of the highest crystal quality reported so far. Under the present growth conditions, the compositions x of the films were automatically settled to be about 0.2 ( Mn 0.8 Sb ) which was determined by electron probe microanalysis and Auger analysis. The Curie temperature, T C , was about 620 K, which was evaluated by the temperature dependence of the magnetization of the film grown on the GaAs substrate. The polar magneto-optical Kerr rotation spectrum of the film on the GaAs substrate was almost the same as that reported previously in the bulk samples. However, the spectrum of the (10.1) film on the GaAs substrate revealed a clearly different structure compared with that of the (00.1) film on the sapphire substrate.

Anisotropic Distribution of Atomic Pairs Induced by the Preferential Resputtering Effect in Amorphous Gd-Fe and Gd-Co Films

Mossbauer effect and X-ray diffraction of amorphous Gd-Fe films show that isolated Gd atoms are preferentially resputtered and a non-uniform distribution of Gd atoms is induced in amorphous Gd-T (T=3d transition metal) films prepared by a sputtering method with negative bias. The resputtering effect of isolated Gd atoms produces anisotropic distributions of T-T, Gd-T and Gd-Gd pairs in Gd-T films. The difference between the numbers of T-T pairs parallel and normal to the film amounts to 1020~1021 pairs/cm3. This number of T-T pairs is appropriate to account for the oserved anisotropy of amorphus Gd-Co films. It is coucluded that the anisotropic distribution of atomic pairs is the most important origin of the magnetic uniaxial anisotropy induced by bias sputtering.

Influence of hydrogen on the magnetic properties of YCo compounds

Abstract The effect of hydrogen absorption on the magnetic properties of the Y2Co7Hx and the YCo3Hx systems was examined in situ. The two systems show similar β and γ phase formation and magnetic behaviour. The β phase exhibits the anomaly that a slight hydrogen enrichment induces a substantial increase in the cobalt moment which varies from a minimum on the low concentration side (0.13 μB in Y2Co7H2 and 0.15 μB in YCo3H) to a maximum on the high concentration side (1.2 μB in Y2Co7H3 and 0.7 μB in YCo3H2). These maximum values are almost equal to those in the respective uncharged compounds. The cobalt moment in the γ phase decreases with increasing hydrogen concentration in the same way as in ordinary cobalt-based ferromagnets. Both systems tend to lose ferromagnetism in the most hydrogenated compounds Y2Co7H8 and YCo3H4. The anomalous dependence of the cobalt moment on composition is discussed.

Annealing effects on magnetic properties of amorphous GdCo, GdFe, and GdCoMo films

Long term thermal stability of the amorphous R‐T films is a fundamental requirement for the sake of practical use. Detailed experiments of the annealing effects were made on the amorphous GdCo, GdFe, and GdCoMo films prepared by means of the D.C. biased r.f. sputtering technique. It is found that annealing at various temperatures reduces Ku, but it enhances Ms and A in all of the films. Moreover, it is found also that the changing rates of Ms and Ku decrease with the increase of Mo concentration in the amorphous GdCoMo films.

In situ observation of the strain of Co and Ni deposited on Pd (111) by reflection high energy electron diffraction

Co/Pd(111) and Ni/Pd(111) bilayer films were grown epitaxially on single crystal MgO (111) substrates by ultrahigh vacuum deposition. In situ observation of the strain of Co and Ni deposited on Pd (111) plane was performed by reflection high energy electron diffraction (RHEED) during fabrication. From RHEED patterns it was confirmed that the lattice constant of a Co film of 2 A in thickness deposited on Pd was about 3.7 A, which was different from that of Pd (3.89 A). The strain (eCo) of the Co layer was rapidly released during further Co deposition. The strain eCo of the third Co monatomic layer on Pd is nearly equal to zero. The large strain of the Co layer is localized at about one or two monatomic layers of the interface between Co and Pd. On the other hand, a Ni film deposited on Pd was not strained from the beginning of the deposition. The relationship between the perpendicular magnetic anisotropy of Co/Pd and Ni/Pd compositionally modulated multilayer films and the strain of Co and Ni is discussed.

In situ measurement of stress in Co/Cu, Co/Pd, and Co/Au compositionally modulated multilayer films

Temporal changes of sign and magnitude of the intrinsic stress during ultra‐high vacuum deposition of Co/Cu, Co/Pd, and Co/Au compositionally modulated multilayer films (CMF’s) were investigated by means of a cantilever technique. The intrinsic stress corresponding to monatomic layers could be detected during deposition. The intrinsic stress in Co layers deposited on Cu, Pd, and Au layers is tensile and the stress of Cu, Pd, and Au layers on Co is compressive. The intrinsic stress of a Co layer on Cu in Co/Cu CMF approaches near to the ideal critical shear stress of the perfect crystal, 1×1011 dyn/cm2.

Magneto-Optical Kerr Rotation Spectra and Perpendicular Anisotropy in Compositionally Modulated Multilayer Films of Co/Pt and Fe/Pt

Magneto-optical Kerr rotation (θK) spectra and magnetic properties such as saturation magnetization (Ms) and perpendicular magnetic anisotropy of Co/Pt and Fe/Pt compositionally modulated multilayer films (CMFs) are investigated. An enhancement of θK is observed at the wavelengths of about 290 and 250 nm in Co/Pt and Fe/Pt CMFs, respectively. It is found that Fe/Pt CMFs turn into perpendicularly magnetized films in the same manner as Co/Pt CMFs when the Fe layer becomes thinner than about 5 A.

Magnetic properties of some gadolinium—Cobalt intermetallic compounds

Abstract Crystallographic and magnetic properties of the single crystals having the compositions of GdCo 3 , Gd 2 Co 7 , GdCo 5 , Gd 2.2 Co 16.6 and Gd 2 Co 17 were studied in order to contribute to the investigation of the magnetic anisotropy in the Gd–Co system. The single crystal used were prepared by means of the Bridgman method using BN-coated alumina crucibles. The room-temperature magnetocrystalline anisotropy constants K 1 of GdCo 3 , Gd 2 Co 7 , GdCo 5 , Gd 2.2 Co 16.6 and Gd 2 Co 17 are determined as 8.1 × 10 6 , 1.3 × 10 7 , 4.1 × 10 7 , 3.0 × 10 6 and -2.7 × 10 6 erg/cm 3 , respectively. it is also found that the magnetocrystalline anisotropy of Gd–Co phases in the stable region of the Th 2 Zn 17 -type structure changes very sensitively from negative to positive as the ratio Gd/Co increases above the stoichiometric ratio of 2/17.