Evaluation of field-induced magnetic moments in the spin-12 antiferromagnetic trimerized chain compound Cu3(P2

Abstract

We report on our evaluation of field-induced magnetic moments in the paramagnetic state of the spin-1 2 antiferromagnetic trimerized (J 1 − J 2 − J 2 ) chain compound Cu 3 (P 2 O 6 OD) 2 with J 1 = 111 K and J 2 = 30 K [M. Hase et al., Phys. Rev. B 76, 064431 (2007)]. Magnetic reflections with integer indices, generated by fieldinduced magnetic moments, were observed at neutron-diffraction experiments performed in an applied magnetic field, and we evaluated the magnitudes of the moments to be M 1 = 0.43(2) μ B /Cu and M 2 = 0.013(10) μ B /Cu on the two crystallographic Cu 2+ (Cu1 and Cu2) sites, respectively, at 6 T and 1.6 K. The resulting ratio M 2 /M 1 = 0.03(2) is in good agreement with the theoretical value for the ratio of the magnetization at the two sites. We thus conclude that for this well-understood spin system (which has the advantage of being amenable to detailed theoretical calculations) the extracted field-induced magnetic moments reproduce the correct information on the magnetization. Our result leads us to believe that we can precisely evaluate exchange interactions in paramagnets with multiple exchange interactions and multiple crystallographic magnetic-ion sites by using field-induced magnetic moments in combination with macroscopic physical quantities. This idea is expected to be applicable to a wide variety of quantum and frustrated magnets without long-range order.

Ground-state phase diagram and thermodynamics of coupled trimer chains

“…In the first case [9][10][11][12][13], the lattice can be divided into two groups with the same number of sites, and the ground state is a gapless singlet. In particular, the magnetic features of the compound Cu 3 (P 2 O 6 OH) 2 are investigated through this model [9,11,14]. In the second case [15][16][17], there are two unit-cell sites in one sublattice and one unit-cell site in the other; thus, a spontaneous break of the rotation symmetry occurs.…”