THERMAL-EXPANSION AND PRESSURE EFFECT ON MAGNETIC TRANSITION OF MN2-XCOXSB

Pressure dependence of the magnetic phase transition temperatures of Mn1.8Co0.2Sb were obtained by measuring temperature variation of initial permeability at various pressure. Both the transition temperature (Tt) from antiferromagnetic (AF) to ferrimagnetic (FM) states and the Curie temperature (Tc) increase with increasing pressure. Temperature variations of the lattice parameters of the sample were also measured by using the powder x-ray diffraction method. The discontinuous change of a and c axes and the changes of the thermal expansion coefficients were observed at Tt and Tc, respectively. It is found that the negative exchange striction below Tc and the sign of volume change at Tt are consistent with the results of pressure dependence of Tc and Tt. On the basis of these results, the relation between the effects of alloying and of pressure on the magnetic transitions of Mn2-xCoxSb system is discussed.