HYPERFINE MAGNETIC-FIELDS AND CURIE-TEMPERATURE IN THE HEUSLER ALLOY NI2MNSN AT HIGH-PRESSURE

The ''hyperfine magnetic field''- H-hpf at the nuclei of the diamagnet ic atoms Sn-119 was measured in Heusler alloy Ni2MnSn by Mossbauer abs orption spectroscopy for pressures up to 10.8 GPa at room temperature. The pressure dependences of H-hpf(Sn) does not show hysteresis and ca n be fitted by linear function H-hpf(Sn)(P)/H-hpf(Sn)(0)=1+k(H) . P wi th the coefficient k(H)=-0.095+/-0.015 GPa(-1), where H-hpf(Sn)(0)=4.6 0+/-0.12T. Diamond anvil cells were used to obtain high pressure at ro om temperature. The Curie temperature (T-C) has been measured (up to 5 .2 GPa) in the ''toroid'' high pressure device using thermal ac suscep tibility measurements. That pressure dependence was linear with the co efficient dT(C)/dP = 7.44 K/Gpa[T-C(0)=341.3 K]. The compressibility o f the sample has been measured by means of resistive strain gauges at hydrostatic pressure up to 9 GPa. The equation (V-V-0)/V-0=-a . P+b . P-2 has been fitted to the experimental data with the coefficients a=8 .64 . 10(-3) GPa(-1), b=1.13 . 10(-4) GPa(-2). The drop of the H-hpf(S n) in pressure range 0-10.8 GPa can be explained on the basis of the e mpirical theory developed by Delyagin, Krylov, and Nesterov [JETP 76, 1049(1980)]. (C) 1996 American Institute of Physics.