Pressure derivatives of Tc in amorphous (Fe100-xMnx)75P15C10 alloys

The pressure dependence of the saturation magnetization and Curie temperature was studied in melt-spun Fe60Mn20B20, Fe56Mn24B20 and Fe75B25 amorphous alloys up to 0.9 GPa, corresponding to volume changes up to 0.45%. In addition, in situ high-pressure (up to 40 GPa) x-ray diffraction was performed to determine the compressibility of the latter two alloys. Both the Curie temperature TC (at atmospheric pressure TC = 201 ± 3 and 159 ± 3 K) and the low-temperature saturation magnetization M5 K,5 T decrease remarkably with increasing pressure: dTC/dp =- 31 ± 0.5 and -32 ± 5 K GPa(-1) and dlnM5 K,5 T/dp =- 0.15 ± 0.02 and -0.13 ± 0.03 GPa(-1) for xMn = 20 and 24 at.%, respectively. Compared to dlnM5 K,5 T/dp =- 0.016 ± 0.003 GPa(-1) measured for Fe75B25, the pressure dependence of M5 K,5 T is one order of magnitude larger in the ternary alloys. The bulk moduli for the Fe56Mn24B20 and Fe75B25 glasses were measured to be 152 GPa and 173 GPa, respectively. These data are also compared with the pressure dependence of the hyperfine field and theoretical calculations of the saturation moment for Fe-B alloys reported in the literature. The results were interpreted within an inhomogeneous itinerant-electron model of ferromagnetism.

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Pressure dependence of magnetic properties in Fe-Mn-B amorphous alloys: evidence for inhomogeneous ferromagnetism

The paper presents the results of measurements of of magnetic properties of some Fe based amorphous alloys The magnetization curves B(H) have been investigated within the range of pressure up to 25 GPa showing considerable changes with pressure The reduction of spontaneous magnetization has been observed due to the pressure shift of Curie temperature In some cases the total disappearence of ferromagnetism with increase of pressure has been observed at isothermal conditions

An influence of pressure on magnetic properties of some amorphous alloys

Amorphous, ferromagnetic, invar like, Fe60 Mn20 B20 alloy has been investigated. Two kinds of experiments were carried out for this alloy. The first, using high pressure technique, revealed the influence of pressure on B(H) dependencies within the wide range of temperature under pressure of 0.5 GPa. From the magnetization curves obtained during these experiments the decrease of spontaneous magnetization caused by applied pressure 0.5 GPa at temperature -180°C has been calculated at the rate about 7 10−11T/Pa. In the second kind of experiments the measurements of volume magnetostriction up to 720 kA/m magnetic field intensity have been done. Volume magnetostriction coefficient at temperature 77.4 K has been determined to be about 2 10−11 [A/m]−1.

J. Schiller

Papers

Pressure dependence of the Curie temperature of amorphous Fe80-xMnxB20 alloys