Magnetic structure and properties of the compositionally complex perovskite (Y0.2La0.2Pr0.2Nd0.2Tb0.2)MnO3

Abstract

Large configurational disorder in compositionally complex ceramics can lead to unique functional properties that deviate from traditional rules of alloy mixing. In recent years, compositionally complex oxides (CCOs) have shown intriguing magnetic behavior including long-range order, enhanced magnetic exchange couplings, and mixed phase magnetic structures. This work focuses on how large local spin disorder affects magnetic ordering in a CCO. Specifically, we investigated the A-site alloyed perovskite, (Y_0.2La_0.2Pr_0.2Nd_0.2Tb_0.2)MnO₃, or (5A)MnO₃, using a combination of bulk magnetometry, synchrotron X-ray diffraction, and temperature-dependent neutron diffraction. The five A-site ions have an average spin and ionic radius nearly equal to that of Nd³⁺ ions, which minimizes structural distortions and allows for an understanding of the local spin disorder effects through a direct comparison with NdMnO₃. Our magnetometry data show that (5A)MnO₃ exhibits two distinct phase transitions associated with the A-site and B-site sublattices, as seen in NdMnO₃, as well as the presence of domain pinning and exchange bias at low temperature, suggesting a mixed phase magnetic ground state, as seen in other magnetic CCOs. Neutron powder diffraction shows clear long-range antiferromagnetic ordering below 67 K and refines to a Pn′ma′ magnetic structure at low temperature, in excellent agreement with the well-studied behavior of NdMnO₃. The two most notable differences in (5A)MnO₃ magnetism apparent from our data are a slight suppression of the B-site ordering temperature, which is explained by a smaller Mn–O–Mn bond angle in (5A)MnO₃ than NdMnO₃, and the presence of a magnetic susceptibility transition above the B-site ordering, which could indicate the formation of a cluster glass but requires further study. This work demonstrates a general method of isolated investigation of size and spin disorder in CCOs and motivates future work using local structure probes to better understand the effects of nanoscale clustering and local spin disorder in magnetic CCOs.