Low-temperature magnetic measurements of an<i>S</i>=1 linear-chain Heisenberg antiferromagnet

Abstract

The temperature-dependent magnetic susceptibility, \ensuremath{\chi}(T), of two pure samples of the S=1 linear-chain Heisenberg antiferromagnet Ni(${\mathrm{C}}_{2}$${\mathrm{H}}_{8}$${\mathrm{N}}_{2}$${)}_{2}$${\mathrm{NO}}_{2}$(${\mathrm{ClO}}_{4}$), commonly known as NENP, has been measured from approximately 300 K to 300 \ensuremath{\mu}K. Our measurements of \ensuremath{\chi}(T) are in agreement with existing results of other researchers who worked above 1.2 K. Below 1.2 K, \ensuremath{\chi}(T) increases with decreasing temperature. The results suggest that the low-temperature increase of \ensuremath{\chi}(T) is not a consequence of a single source of paramagnetic impurities in the samples but may arise from S=1/2 end-chain interactions.