On the pressure and temperature dependence of ordering temperature and magnetization of Y1−xThxCo4B compounds

Abstract

We present here a detailed investigation of the pressure dependence of the structural and magnetic properties in a wide temperature range from 5 to 340 K for the Y1−xThxCo4B series. The unit cell lattice compressibility has been determined from powder neutron diffraction technique in the 0 to 0.5 GPa pressure range. Substitution of Th for Y is found to reduce significantly the compressibility. The Curie temperature decreases dramatically upon the Th for Y substitution. Studies were performed on polycrystalline samples under hydrostatic pressure up to 1.1 GPa and in magnetic field up to 5 T. The evolution of the saturation magnetization under pressure is presented as well as the pressure dependence of the Curie temperature. Remarkable pressure effects on the Curie temperature and on the critical field at which the first order magnetization process occurs for Y0.8Th0.2Co4B are analyzed and discussed. The pressure derivatives values of both the Curie temperature and the magnetization are negative for all the studied compounds. This is an opposite tendency than that expected from chemical pressure effects. This supports the dominant role of valence electrons in the magnetic properties of the substituted Y1−xThxCo4B compound in the case of the chemical pressure effect. The magnetization and the Curie temperature exhibit different pressure dependence along the Y1−xThxCo4B series of compounds.