Large Magnetocaloric Effect at the Saturation Field of an S=1/2 Antiferromagnetic Heisenberg Chain
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Abstract
We report low-temperature magnetization measurements on a copper-containing coordination polymer [Cu(μ-C2O4)(4-aminopyridine)2(H2O)] n . According to these measurements and previous results (Prokofiev et al. in Cryst. Res. Technol. 42, 394, 2007), the material is a very good realization of an S=1/2 antiferromagnetic Heisenberg chain with a small saturation field B s =4.2 T, which marks the endpoint of a quantum-critical line in the B–T plane. Measurements of the magnetocaloric effect at low temperatures T=0.47 K across the saturation field yields a very large magnetothermal response with a characteristic sign change close to the quantum-critical point. The data are in good agreement with the quantum-critical behavior calculated on the basis of exact diagonalization and quantum Monte Carlo simulations.
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