Structural and magnetic alteration of Cu2GaBO5 forced by Mn3+ doping

https://doi.org/10.1016/j.jallcom.2022.163822

To study the gradual change of the structure and the magnetic state of the ludwigite Cu2GaBO5 upon Mn3+ doping, single crystals of Cu2Ga1−xMnxBO5 (x = 0.55, 0.7, 0.8) with the size up to 3 × 3 × 10 mm3 were grown using the flux technique. The phase homogeneity and crystal structure of the obtained compounds were investigated by the powder and single crystal X-ray diffraction. All the samples possessed the monoclinic-distorted ludwigite structure with the P21/c space group. The study of the actual Cu/Ga/Mn composition by the EDX (energy-dispersive X-ray spectroscopy) technique revealed the lower Mn content in all the samples and the refined formulas were Cu2Ga0.47Mn0.53BO5, Cu1.92Ga0.5Mn0.58BO5 and Cu2Ga0.32Mn0.68BO5, respectively. Despite the high manganese content, the concentration transition (from Cu2GaBO5 to Cu2MnBO5) and change of the monoclinic angle did not occur, but strong Me-O octahedra distortions exceeding those both in the parent ludwigites Cu2GaBO5 and Cu2MnBO5 were found. The study of the thermodynamic and magnetic properties revealed the low-temperature magnetic phase transition inherited from the parent Cu2GaBO5 in all the samples. However, the nature and ordering type for the compounds with different Mn content were different: there was a complex transformation of the magnetic state from the partially ordered AFM (antiferromagnetically) in Cu2Ga0.47Mn0.53BO5, through the spin glass state, to the combined spin glass/ordered state in Cu2Ga0.32Mn0.68BO5 with the appearance of magnetic anisotropy. The evident dependence of Tc (phase transition temperature) on the magnetic field was found as well as its decrease at the nonzero magnetic field in the samples with x = 0.53 and 0.68.