H. Onodera

Magnetic inhomogeneity in amorphous Fe-Zr alloys

Abstract Magnetic properties of amorphous Fe92Zr8 and Fe90Zr10 alloys have been studied by 57Fe Mossbauer and magnetization measurements. The magnetic hyperfine field distribution spreads over a wide range and the temperature dependence of the hyperfine fields shows magnetically heterogeneous behavior. Superparamagnetic behavior was observed on the magnetization curves above Tc.

Structural and magnetic properties of Ni2In type (Mn1 − xNix)65Ga35 compounds

Abstract New intermetallic compounds (Mn 1 − x Ni x ) 65 Ga 35 of Ni 2 In type structure are found in the range of 0.15 ⩽ x ⩽ 0.45. In the higher x range, the magnetization—temperature curves show Curie—Weiss type behaviors, but those with x ⩽ 0.35 suggest another type ferromagnet. The magnetic ordering temperature T c decreases for x ⩽ 0.2 and then increases with increasing x . The curves of 0.25 ⩽ x ⩽ 0.3 show a hump and then slightly decrease with decreasing temperature. In the neutron diffraction experiment for x = 0.275, the (0 0 1) reflection appears for 165 K ⩽ T T C to 8.47 C with temperature.

Structure and magnetic properties of FenCrnN sputter-deposited films

Structure and magnetic properties of FenCrnN ternary films prepared by DC magnetron facing-target sputtering have been investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), vibrating sample magnetometry (VSM) and Mossbauer effect. These films exhibit perpendicular magnetic anisotropy. We found that N2-to-Ar flow ratio, Fe-Cr target area ratio and substrate temperature during film preparation are the factors influencing the anisotropy. Adjusting the chemical composition and deposition parameters, we obtained saturation magnetization of 300–400 emu/cm3 and perpendicular coercivity of 800–1100 Oe. XRD measurements show that the films generally consist of the α-Fe(Cr) and γ′-(Fe,Cr)4Nx (x < 1) phases, and that the enhancement of perpendicular anisotropy is always accompanied by a decrease in the grain size of α-Fe(Cr) phase and growth of the γ′-(Fe,Cr)4Nx phase with a pronounced (2 0 0) texture. The Mossbauer spectra show that the γ′-(Fe,Cr)4Nx phase is nonmagnetic at room temperature. Using the SEM and TEM, we found that the nonmagnetic γ′-(Fe,Cr)4Nx phase displays columnar growth and that the small ferromagnetic α-Fe(Cr) grains of about 2–20 nm in diameter are located at grain boundaries of γ′-(Fe,Cr)4Nx grains. Shape anisotropy seems to play an important part in the perpendicular magnetic anisotropy in these FenCrnN films.

Magnetic properties of (Ni1-xMnx)1.9Ge Alloys

Abstract The high-temperature phase of (Ni 1 - x Mn) 1.9 Ge is found to be a hexagonal Ni 2 In type structure in the range 0 ⩽ x ⩽ 0.7. In the lower values of x , spin glass and re-entrant spin-glass phase was found. In the range 0.55 ⩽ x ⩽ 0.7, the alloys are ferromagnetic and the Curie temperature decreases with increasing x . A phase transition of Ni 2 In type ⇔TiNiSi type occurs at 0.45 ⩽ x ⩽ 0.55, below 270K. Magnetic and crystallographic phase diagram is proposed.

Magnetic phase transitions in DyMn2Ge2 studied by neutron diffraction

Abstract The magnetic phase transitions in DyMn 2 Ge 2 were studied by neutron diffraction. The (111) antiferromagnetic order reflection due to Mn atoms is observed only above 40 K, and the intermediate superlattice (110) ± line is observed in the temperature range between 35 and 40 K. It is concluded that the intermediate temperature phase is a magnetically single phase in which the magnetic stracture is described with a propagation vector k ≈ (0, 0, 0.65).

Magnetic properties of (Fe1-xMnx)3Ga

Abstract We have found that the ferromagnetic alloys (Fe 1- x ,Mn x ) 3 Ga of a D0 3 -type structure are stable up to x = 0.5. A partially ordered L2 1 -type structure is confirmed by neutron diffraction experiments. The magnetization decreases monotonically with increasing x . The Curie temperature has a minimum value of 200 K at x = 0.35. The average magnetic moment per (Fe or Mn) atom in the 4b site keeps nearly a constant value of 1.7 μ B , and that in the 8c site decreases rapidly with increasing x , showing negative valules for x ⩾ 0.4. In addition to the saturation magnetization, large paramagnetic components are observed in high magnetic fields.