Hindered Rotation of Methyl Groups in CaCu(CH₃COO)₄·6H₂O and CaCu(CD₃COO)₄·6H₂O at Low Temperatures

Abstract

The specific heat of CaCu(CH 3 COO) 4 ·6H 2 O has been measured between 0.3 and 8 K. The present result showed the Schottky anomaly, which was analyzed to be due to the hindered rotation of CH 3 groups. The validity of present hypothesis was evidenced by the specific heat measurements of the deuterated sample CaCu(CD 3 COO) 4 ·6H 2 O between 0.25 and 1.0 K. From the specific heat measurements, energy splitting Δ E / k B is estimated as 2.57±0.02 K for CaCu(CH 3 COO) 4 ·6H 2 O and 0.24±0.03 K for CaCu(CD 3 COO) 4 ·6H 2 O.