Magnetic structures of the rare-earth quadruple perovskite manganites RMn7O12

Abstract

We report a neutron powder diffraction study of RMn7O12 quadruple perovskite manganites with R = La, Ce, Nd, Sm, and Eu. We show that in all measured compounds concomitant magnetic ordering of the A and B manganese sublattices occurs on cooling below the Néel temperature. The respective magnetic structures are collinear, with one uncompensated Mn 3+ moment per formula unit as observed in bulk magnetisation measurements. We show that both LaMn7O12 and NdMn7O12 undergo a second magnetic phase transition at low temperature, which introduces a canting of the B site sublattice moments that is commensurate in LaMn7O12 and incommensurate in NdMn7O12. This spin canting is consistent with a magnetic instability originating in the B site orbital order. Furthermore, NdMn7O12 displays a third magnetic phase transition at which long range ordering of the Nd sublattice modifies the periodicity of the incommensurate spin canting. Our results demonstrate a rich interplay between transition metal magnetism, orbital order, and the crystal lattice, which may be fine tuned by cation substitution and rare earth magnetism.

Emergence of a Magnetostructural Dipolar Glass in the Quadruple Perovskite Dy1−δMn7+δO12<

“…To establish the microscopic origin of the observed phase transitions, NPD data were collected in the paramagnetic phase above T C [ Fig . Every diffraction peak observed in the paramagnetic phase could be accounted for by the I2=m crystal structure common to many RMn 7 O 12 compounds [16][17][18][19], indicating that the sample was single phase (consistent with laboratory based x-ray diffraction measurements [20]). Rietveld refinement of the respective structural parameters (Table I) including A-site cation disorder gave an excellent fit to the data, as shown in On cooling through T C additional diffraction intensities appeared that could be indexed with the Γ point, k ¼ ð0; 0; 0Þ propagation vector.…”

“…Rietveld refinement of the respective structural parameters (Table I) including A-site cation disorder gave an excellent fit to the data, as shown in On cooling through T C additional diffraction intensities appeared that could be indexed with the Γ point, k ¼ ð0; 0; 0Þ propagation vector. These intensities were well accounted for by a collinear ferrimagnetic structure composed of all Mn moments, as found below T C in most other RMn 7 O 12 compounds [19,21]. Refinement of this magnetic structure against data measured at 20 K [ Fig.…”

Origin of negative magnetization phenomena in (Tm1−xMnx)MnDönni1, Pomjakushin2, Zhang3 et al. 2020Phys. Rev. B111100View full textAdd to dashboardCite

“…75% of doping can result in the so-called A-site-ordered quadruple perovskites with a general composition of AA 3 B 4 O 12 , where a square-planar A site is usually occupied by Cu 2+ , Mn 2+ , and Mn 3+ [14]. The interaction between 3d transition metals located at the A and B sites can be strong resulting in simultaneous magnetic ordering of cations at these sites, for example, in AMn 7 O 12 (A = Cd, Ca, Sr, and Pb) [15], RMn 7 O 12 [16], and RCu 3 Mn 4 O 12 [17]. But the A sublattice still shows weaker coupling if it is occupied by magnetic rare-earth cations.…”

“…But the A sublattice still shows weaker coupling if it is occupied by magnetic rare-earth cations. For example, Mn 3+ cations at both A and B sites are ordered at T N,Mn = 85 K in NdMn 7 O 12 , while Nd 3+ cations at the A site are ordered at T N,Nd = 8.5 K [16]; T N,Mn = 108 K in DyMn 7 O 12 , while T N,Dy = 8.5 K [18]; T N,Mn/Cu = 395 K in TbCu 3 Mn 4 O 12 , while T N,Tb ∼ 60 K [17].…”

Tunable ferrimagnetic-antiferromagnetic response by the inclusion of Fe in the gadolinium-based manganite GdMnO3

“…Particularly, family of manganites which are based on rare-earth elements have been extensively studied in recent years, because their properties mainly associated with the interaction between the rare-earth-4f orbitals and the Mn-3d orbitals, which give rise to very interesting magnetic behaviors and electrical transport properties [5]. This kind of material are recognized because evidence properties as antiferromagnetism [6], ferroelectric response, spontaneous or induced by magnetic fields [7], magnetoelectricity [8], giant and colossal magnetoresistance [9], and exchange interactions involving the Mn 3+ and R 3+ (rare-earth) magnetic moments [10].…”