Effect of Impurity Spins on Three-Dimensional Ordering of TMMC under Magnetic Field

Abstract
The phenomena of rapid increase of the Néel temperature T N ( H ) of the quasi-one-dimensional antiferromagnet TMMC ( T N (0)=0.835 K) has been studied by the heat capacity measurement under the magnetic field H perpendicular to c -axis; T N ( H )/ T N (0)≃2 at H =30 kG. On the contrary, T N ( H ) for the impure TMMC with 0.44 atom-% Cu 2+ ions keeps to stay near T N (0)=0.74 K independently of the field. The possible correlation length along the magnetic chain is discussed.