Magnetoelastic and magnetothermal properties of low-dimensional quantum spin systems in high magnetic fields—a case study

Abstract

We report measurements of magnetic, magnetothermal and magnetoelastic properties of a new Cu(II)-coordination polymer Cu(II)-2,5-bis(pyrazol-1-yl)-1,4-dihydroxybenzene (CuCCP). According to our results which cover wide ranges of temperatures 0.06K⩽T⩽320K and magnetic fields B⩽50T, this material presents an almost ideal realization of an one-dimensional uniform S=12 Heisenberg antiferromagnet. Owing to the moderate exchange-coupling constant of |J|/kB=21.5K, it was possible to study the system in its interesting high-field range, i.e., across the saturation field gμBBs=2|J|, which, at T=0, marks the endpoint of a quantum critical line. Using pulse-field techniques the high-field magnetization and elastic constant have been measured. A comparison with calculated magnetization curves reveals a distinct magnetocaloric effect at high fields for T<7.5K, which grows upon cooling. In addition, at temperatures T<|J|/kB, a pronounced acoustic anomaly has been found close to Bs and identified as a generic property of the uniform antiferromagnetic Heisenberg chain with a finite spin–lattice interaction.