Evolution from 4f-electron antiferromagnetic to ferromagnetic order in the CeCu(Ge1-xSnx) alloy series (0≤x≤1)

Abstract

We report the evolution from ferromagnetic (FM) to antiferromagnetic (AFM) state in CeCu(Ge1-xSnx) investigated by means of magnetic and heat capacity measurements. X-ray diffraction studies for all compositions indicate the ZrBeSi - type hexagonal crystal structure with space group P63/mmc (No. 194). The magnetic susceptibility, x(T) at high temperature follows the Curie - Weiss relation with an effective magnetic moment close to the value of 2.54 µB expected for free Ce3+ - ion. At low temperatures, x(T) data indicate AFM transition for alloys in the concentration range 0.7≤x≤1 and FM for x≤0.6. The magnetization, M(µ0H) of samples exhibiting AFM behaviour shows metamagnetic transition at low magnetic fields with some irreversibility in the process of increasing and decreasing magnetic field. In turn, M(µ0H) of samples exhibiting FM behaviour shows saturation in high magnetic fields. Heat capacity, Cp(T) data confirm the AFM and FM transitions observed in magnetic measurements. An additional anomaly below TC and TN is observed in Cp(T)/T, which likely arises from spin reorientation or rearrangement in FM or AFM structure. Below in FM region, Cp(T) can be well described assuming spin-waves excitations with an energy gap ∆C.