Effect of spin fluctuations on thermal expansion characteristics in paramagnetic Laves-phase Lu(Co_(1-x)Ga_x)_2 compounds

摘要

The examination of thermal variation of the amplitude of spin fluctuations in exchange-enhanced Pauli paramagnetic Laves-phase Lu(Co_(1-x)Ga_x)_2 compounds with x ≤ 0.09 has been concerned with the thermal expansion characteristics. The thermal expansion coefficient α shows a significant concentration dependence. The temperature dependence of the spontaneous volume magnetostriction ω_(mag) significantly increases and its increment becomes steeper with increasing x. This means that low-temperature spin fluctuation excitation becomes significant on coming close to the critical concentration for the onset of ferromagnetism. Associated with the change of spin fluctuation characteristics, the magnetovolume coupling constant kC_(mv) decreases with increasing x. The amplitude of spin fluctuations at the magnetic susceptibility maximum temperature T_(max) < ξ~2(T_(max)>)~(1/2), obtained from ω_(mag) at T_(max), becomes almost constant at 0.37μ_B per Co atom. This behavior indicates that the magnetic susceptibility maximum phenomenon can be attributed to the thermal variation of the amplitude of spin fluctuations.