Specific heat and thermal expansion characteristics related to spin fluctuations in antiferromagnetic beta-MnOs alloys

The temperature dependences of magnetic susceptibility, the specific heat a nd the thermal expansion of beta -Mn1-xOsx alloys have been investigated. T he electronic specific heat coefficient gamma is significantly large and dr astically decreases with increasing x. The specific heat peak associated wi th the Neel temperature T-N is clearly observed in high Os concentration re gions. On the other hand, in low Os concentration regions, the peak is not clear and a linear relation between gamma and T-N(3/4) is observed. Therefo re, it is concluded that beta -Mn1-xOsx alloys with low x are weak itineran t-electron antiferromagnets. The thermal expansion coefficient alpha in the paramagnetic state is remarkably large in the low Os concentration regions and becomes smaller with increasing x; that is, the larger the electronic specific heat coefficient gamma, the larger the value of alpha in the param agnetic regions.