Magnetovolume effects and spin fluctuations in Mn3+xRh1−xalloys

Abstract

The electrical resistivity, thermal properties, pressure effect on the Néeltemperature and compressibility of Mn3+xRh1−x (x = 0.0, 0.12,0.20 and 0.32) alloys have been investigated in order to discuss the magnetovolume effectsin both ordered and disordered states. The electronic specific heat coefficient γexp of theMn3Rhordered alloy is slightly smaller than that of the disordered one,qualitatively consistent with the theoretical calculations. A negativemagnetovolume effect is observed below the Néel temperatureTNin both the ordered and disordered alloys. Furthermore, the magneticcontribution to the thermal expansion is significant even in theparamagnetic region. That is, the thermal expansion coefficient α inthe paramagnetic region shows a large value of about 30 × 10−6 K−1,because of a significant contribution from spin fluctuations. For the Mn3Rhordered alloy, the pressure shift of the Néel temperature, dTN/dP, is estimated to be about7.0 K GPa−1.The temperature dependence of α exhibits a pronouncedpositive peak at TNin accordance with the positive pressure dependence ofTN.A large compressibility of 1.4 × 10−2 GPa−1has been obtained from the change in the lattice constant under pressure.