Concentration transition in Cu2(Mn,Ga)BO5 solid solutions

• Published in: Journal of magnetism and magnetic materials 2023-10, Vol.584, p.171072, Article 171072
• Main Authors: Moshkina, Evgeniya, Eremin, Evgeniy, Veligzhanin, Alexey, Pavlovskiy, Maksim, Sofronova, Svetlana, Titova, Veronika, Bezmaternykh, Leonard
• Format: Article
• Language: English
• Subjects: Ludwigite; Magnetic phase transition; Solid solution; Spin glass state
• ISSN: 0304-8853
• DOI: 10.1016/j.jmmm.2023.171072

•Magnetic properties of Cu2Mn1-xGaxBO5 (x = 0.04, 0.11, 0.17, 0.25) single crystals are studied in detail.•The critical concentration of Cu2MnBO5 → Cu2GaBO5 concentration phase transition was found in the range x  = 0.17–0.25.•The compounds of the transition range inherited the properties of both parent Mn- and Ga-ludwigites, that manifest as complex pattern of magnetic phase transitions.•The sequental multiple phase transitions at narrow temperature ranges were found in all samples with different frequency and orientational dependence.•An evidence of the separate ordering of different magnetic subsystems were found. The effects related to the conversion of magnetic structures of a Cu2MnBO5 ferrimagnet to a Cu2GaBO5 antiferromagnet under the Mn3+ → Ga3+ substitution were studied. The properties of four single crystal samples with the gallium concentration x  = 0.04, 0.11, 0.17, 0.25 were examined. The chemical composition and valence state of the samples were determined by X-ray absorption spectroscopy element-sensitive technique. Distribution of the 3d metal ions over crystallographic positions was studied using the first principle calculations by Wien2k program. The evolution of the magnetic properties was investigated by the measurements of the temperature and field dependences of magnetization, dc and ac magnetic susceptibility. In agreement with the previous study of the structure evolution of Cu2Mn1-xGaxBO5 solid solutions, the critical concentration upon a change in the magnetic ordering type was found in the range x  = 0.17–0.25. The non-monotonic behavior of magnetization in terms of the gallium content was found in the concentration range of 0.04–0.17. A complex pattern of magnetic phase transitions belonging to the concentration phase boundary was obtained in the compounds with gallium being within the range x  = 0.17–0.25. One could observe the splitting of the peaks of the real part of ac-susceptibility of the high-temperature phase transition in the Cu2MnBO5-like phase (x = 0.04, 0.11) and that of the low-temperature one at the concentration boundary (x = 0.17, 0.25) with different frequency and orientational dependence. The type and origin of the multiple phase transitions observed in the studied samples were analyzed.