engleski

Site-Specific Spin Reorientation in Antiferromagnetic State of SeCuO3

We report on magnetic field induced spin reorientation in antiferromagnetically (AFM) ordered state of low-dimensional magnet SeCuO3 observed by torque magnetometry experiment. Monoclinic SeCuO3 was reported to be quasi-isolated linear spin tetramer system Cu2-Cu1-Cu1-Cu2 where strong Cu1-Cu1 interaction leads to spin singlet formation. Below TN=8K AFM long-range order (LRO) sets in. The question arises whether spin singlet persists in LRO state or is broken allowing Cu1 spins to participate in the LRO state. We performed extensive torque magnetometry measurements in AFM state of SeCuO3. We employ simple phenomenological model using symmetry allowed magnetocrystalline anisotropy energy (MAE) to simulate spin reorientation and measured torque. This approach can quantitatively describe our data only under assumption of partial spin reorientation. Based on these results, we propose a model of magnetic order in H=0 and in H>HSF. The microscopic origin of MAE in SeCuO3 was also investigated using DFT+U calculations including spin-orbit coupling on an AFM model. It was evidenced inequivalent Cu sites impact differently the magnetic anisotropy of this system. Our results suggest that Cu1 singlets persist even in AFM LRO state, and only Cu2 spins reorient in finite magnetic field. This work is fully supported by the Croatian Science Foundation (grant UIP-2014-09-9775) and by the COGITO project Theoretical and experimental study of magnetic and multiferroic materials.

Magnetic anisotropy, spin reorientation, low-dimesional spin systems

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