Criticality-Enhanced Magnetocaloric Effect in Quantum Spin Chain Material Copper Nitrate.

In this work, a systematic study of Cu(NO)·2.5 HO (copper nitrate hemipentahydrate, CN), an alternating Heisenberg antiferromagnetic chain model material, is performed with multi-technique approach including thermal tensor network (TTN) simulations, first-principles calculations, as well as magnetization measurements. Employing a cutting-edge TTN method developed in the present work, we verify the couplings J = 5.