Nonlinear Pressure Dependence of the Curie Temperature in (Cr_1-yV_y)₅Te₈ and (Cr_1-xTi_x)₅Te₈

Abstract

It is known that Cr₅Te₈, V₅Te₈ and Ti₅Te₈ are ferromagnetic, weakly or nearly antiferromagnetic, and Pauli-paramagnetic materials, respectively. The temperature dependence of magnetization in (Cr_1-yV_y)₅Te₈ is measured, from which the magnetic phase diagram and the generalized Curie-Weiss (GCW) parameters are investigated. Gross feature of dT_C(Curie temperature)/dy<0 is similar to that of dT_C/dx<0 in (Cr_1-xTi_x)₅Te₈, except dT_C/dy ≅ 0 near y=0. No qualitative difference in the GCW parameters is observed in the low ranges of y and x. The pressure (P) dependence of T_C for the low ranges of y and x is investigated by measuring permeability. The observed nonlinear P-dependence of T_C is systematically described with T_C,P=T_C,P=0 [1+ζP ] [1+ηP ]² for η < 0 and ζ > 0 with dη/dy < 0, dη/dx < 0, d ζ/dy>0 and dζ/dx > 0. The GCW, T_C,P=0, η and ζ parameters are connected to the spin fluctuation model for itinerant electron ferromagnetism proposed by Moriya. The obtained y and x dependence of GCW, T_C,P=0, η and ζ parameters is discussed on the view-point of the difference in electron correlation natures and magnetic states of Cr₅Te₈, V₅Te₈ and Ti₅Te₈.