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

摘要

We report the evolution from ferromagnetic (FM) to antiferromagnetic (AFM) state in CeCu ( Ge 1 ? x Sn x ) 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, χ ( T ) at high temperature follows the Curie - Weiss relation with an effective magnetic moment close to the value of 2.54 μ B expected for free Ce 3 + - ion. At low temperatures, χ ( T ) data indicate AFM transition for alloys in the concentration range 0.7 ≤ x ≤ 1 and FM for x ≤ 0.6 . The magnetization, M ( μ 0 H ) 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 ( μ 0 H ) of samples exhibiting FM behaviour shows saturation in high magnetic fields. Heat capacity, C_p(T) data confirm the AFM and FM transitions observed in magnetic measurements. An additional anomaly below T_C and T_N is observed in C_p(T)/T, which likely arises from spin reorientation or rearrangement in FM or AFM structure. Below in FM region, C_p(T) can be well described assuming spin-waves excitations with an energy gap Δ C .