EPR-Determined Anisotropy of the g-Factor and Magnetostriction of a Cu2MnBO5 Single Crystal with a Ludwigite Structure

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Electron paramagnetic resonance (EPR) and magnetostriction of the Cu₂MnBO₅ single crystal have been studied. The EPR spectrum consists of a single Lorentzian line due to the exchange-coupled system of spins of Cu²⁺ and Mn³⁺ ions. It has been established experimentally that the g-factor in the paramagnetic region is strongly anisotropic and anomalously small, which is not typical of the exchange-coupled system of spins of Cu²⁺ and Mn³⁺ ions. At a temperature of 150 K, the g-factors along the crystallographic a, b, and c axes are 2.04, 1.96, and 1.87, respectively. Such small effective g-factor values can be due to the effect of the anisotropic Dzyaloshinskii–Moriya exchange interaction between the spins of Cu²⁺ and Mn³⁺ ions directed along the a axis. The presence of two Cu²⁺ and Mn³⁺ Jahn–Teller ions occupying four nonequivalent positions in the crystal is responsible for the absence of the inversion center. It is found that the behavior of the magnetostriction of Cu₂MnBO₅ is not typical of transition-metal crystals but is closer to the behavior of crystals containing rare-earth ions.