We report on the successful high-pressure synthesis of single-phase powders of the quadruple perovskite (YMn3) Mn4O12, where the chemical pressure exerted by the small Y3+ ion is expected to enhance the exchange interaction between Mn3+ ions. According to this expectation, powder neutron diffraction, specific heat, and magnetization measurements give evidence of a C-type antiferromagnetic ordering of the Mn3+ ions in the octahedrally coordinated B sites at T-N,T-B = 108 K, 30 K higher than in the isostructural and isovalent compound, (LaMn3) Mn4O12. Surprisingly, we found no evidence of long-range magnetic order of the square-coordinated A' sites, although an indication of latent magnetic order is given by a broad peak of the DC magnetization between 70 and 40 K and by a sharp peak in the AC susceptibility at T* = 70 K. A further unexpected feature of (YMn3) Mn4O12, not found in previously reported (AMn(3)) Mn4O12 compounds, is a second-order structural phase transition at T-s = 200 K, attributed to a partial redistribution of charge involving both the B and A'-site Mn3+ ions. The present results suggest the existence of competing magnetic orderings, which may be linked to the occurrence of magnetic ferroelectricity in the (AMn(3)) Mn4O12 system.
Effect of chemical pressure induced by La3+/Y3+ substitution on the magnetic ordering of (AMn(3)) Mn4O12 quadruple perovskites
Mezzadri F;Delmonte D;Gilioli E;
2017
Abstract
We report on the successful high-pressure synthesis of single-phase powders of the quadruple perovskite (YMn3) Mn4O12, where the chemical pressure exerted by the small Y3+ ion is expected to enhance the exchange interaction between Mn3+ ions. According to this expectation, powder neutron diffraction, specific heat, and magnetization measurements give evidence of a C-type antiferromagnetic ordering of the Mn3+ ions in the octahedrally coordinated B sites at T-N,T-B = 108 K, 30 K higher than in the isostructural and isovalent compound, (LaMn3) Mn4O12. Surprisingly, we found no evidence of long-range magnetic order of the square-coordinated A' sites, although an indication of latent magnetic order is given by a broad peak of the DC magnetization between 70 and 40 K and by a sharp peak in the AC susceptibility at T* = 70 K. A further unexpected feature of (YMn3) Mn4O12, not found in previously reported (AMn(3)) Mn4O12 compounds, is a second-order structural phase transition at T-s = 200 K, attributed to a partial redistribution of charge involving both the B and A'-site Mn3+ ions. The present results suggest the existence of competing magnetic orderings, which may be linked to the occurrence of magnetic ferroelectricity in the (AMn(3)) Mn4O12 system.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.