High-field magnetization and magnetic phase diagram of α−Cu2V2O7

Abstract

14High-field magnetization of the spin-1/2 antiferromagnet α-Cu2V2O7 was measured in pulsed magnetic fields of up to 56 T in order to study its magnetic phase diagram. When the field was applied along the easy axis (the a-axis), two distinct transitions were observed at Hc1 = 6.5 T and Hc2 = 18.0 T. The former is a spin-flop transition typical for a collinear antiferromagnet and the latter is believed to be a spin-flip transition of canted moments. The canted moments, which are induced by the Dzyaloshinskii-Moriya interactions, anti-align for Hc1 < H < Hc2 due to the anisotropic exchange interaction that favors the antiferromagnetic arrangement along the a-axis. Above Hc2, the Zeeman energy of the applied field overcomes the antiferromagnetic anisotropic interaction and the canted moments are aligned along the field direction. Density functional theory was employed to compute the exchange interactions, which were used as inputs for quantum Monte Carlo calculations and then further refined by fitting to the magnetic susceptibility data. Contrary to our previous report in Phys. Rev. B 92, 024423, the dominant exchange interaction is between the third nearest-neighbor spins, which form zigzag spin-chains that are coupled with one another through an intertwining network of the nonnegligible nearest and second nearest-neighbor interactions. In addition, elastic neutron scattering under the applied magnetic fields of up to 10 T reveals the incommensurate helical spin structure in the spin-flop state.

Spin Seebeck effect in the polar antiferromagnet α−Cu2V2O7

“…As illustrated in Fig. 1(a), all Cu 2+ ions form two sets of almost perpendicular zigzag chains [6][7][8][9].Magnetic properties of α-Cu 2 V 2 O 7 are governed by Cu 2+ S = 1/2 spins, since V 5+ ions are nonmagnetic. In the proposed spin Hamiltonian [10], there are three important terms to explain the magnetic properties of α-Cu 2 V 2 O 7 .…”

“…As illustrated in Fig. 1(a), all Cu 2+ ions form two sets of almost perpendicular zigzag chains [6][7][8][9].…”

“…In the zigzag spin chains, Cu 2+ spins interact with their nearest neighbors. Since the magnetic interactions between nearest (J 1 ), second-nearest (J 2 ), and third-nearest (J 3 ) neighbors are all antiferromagnetic [6][7][8][9][10], α-Cu 2 V 2 O 7 exhibits antiferromagnetism. The second term is an anisotropic exchange interaction, which arises from the multiorbital correlation effect [10].…”

“…The clear observation of the SSE in antiferromagnetic α-Cu 2 V 2 O 7 allows us to test the theoretical models proposed for the antiferromagnetic SSE [16,17]. Using the magnon spin current theory [17] combined with magnetic parameters determined by previous neutron experiments for α-Cu 2 V 2 O 7 [8-10], we demonstrated that temperature and magnetic-field dependences of magnon lifetimes are important for the antiferromagnetic SSE in α-Cu 2 V 2 O 7 |Pt systems.Single crystals of α-Cu 2 V 2 O 7 were grown by a vertical Bridgman method following the previous reports [8][9][10]. …”

“…Single crystals of α-Cu 2 V 2 O 7 were grown by a vertical Bridgman method following the previous reports [8][9][10].…”