Magnetic structure and spin-flop transition in the A -site columnar-ordered quadruple perovskite TmMn3O6

Abstract

We present the magnetic structure of TmMn3O6, solved via neutron powder diffraction -the first such study of any RMn3O6 A-site columnar-ordered quadruple perovskite to be reported. We demonstrate that long range magnetic order develops below 74 K, and at 28 K a spin-flop transition occurs driven by f -d exchange and rare earth single ion anisotropy. In both magnetic phases the magnetic structure may be described as a collinear ferrimagnet, contrary to conventional theories of magnetic order in the manganite perovskites. Instead, we show that these magnetic structures can be understood to arise due to ferro-orbital order, the A, A and A site point symmetry, mm2, and the dominance of A-B exchange over both A-A and B-B exchange, which together are unique to the RMn3O6 perovskites. arXiv:1901.06874v1 [cond-mat.str-el]

Effects of magnetic dilution in the ferrimagnetic columnar ordered Sm2MnMnMn4−xTixO12Vibhakar1, Khalyavin2, Manuel3 et al. 2020Phys. Rev. B6000View full textAdd to dashboardCite

“…The refined magnetic structure is consistent with the collinear ferrimagnetic phase found in Tm 2 MnMnMn 4 O 12 [17] and R 2 CuMnMn 4 O 12 [18]. Moment orientations of m||[x, 0, 0], m||[x, x, 0], or m||[x, y, 0] correspond to different magnetic symmetries described by the three distinct order-parameter directions of the + 5 irrep (see Tables III, IV, and V of Appendix A); however, these three cases cannot be differentiated by our neutron-diffraction data due to powder averaging in the tetragonal crystal symmetry.…”

“…Here, both A-B and B-B d-d superexchange interactions are present, and the a + a + c − tilts remove A-A d-d superexchange pathways, which are then reduced to super-superexchange. The weakness of A-A d-d exchange has recently been demonstrated in (NaDy)MnMnTi 4 O 12 [16], where in the absence of A-B and B-B interactions (B = Ti 4+ ), antiferromagnetic order develops on the A-site sublattices only below 12 K. To the contrary in Tm 2 MnMnMn 4 O 12 , the presence of both A-B and B-B exchange stabilizes ferrimagnetic order below 74 K, with a ferromagnetic B-site sublattice that is in direct contradiction to the C-type antiferromagnetic B-site sublattice theoretically predicted by B-B exchange alone-a state that is instead thought to arise as a result of A-B exchange dominating over both A-A and B-B exchange [17]. Indeed, it was shown that when A-B exchange is weakened by substituting Cu 2+ for Mn 3+ on the A sites (R 2 CuMnMn 4 O 12 , R = Dy and Y), antiferromagnetic spin canting is introduced onto the B-site sublattice [18].…”

“…In this paper, we report the tuning of magnetic exchange interactions in the Sm 2 MnMnMn 4−x Ti x O 12 A-site columnar ordered quadruple perovskite manganites by chemical substitution of nonmagnetic Ti 4+ for B-site Mn 3+ for x = 1, x = 2, and x = 3. This series interpolates between the A-site-only, antiferromagnetic structure of (NaDy)MnMnTi 4 O 12 [16] [15,17] has been suppressed by the B-site chemical disorder [19]. The three symmetry-inequivalent A sites, shown in Fig.…”

“…The Jahn-Teller active Mn 3+ ions present in the x = 1 and x = 2 samples are expected to impose an average weak single-ion anisotropy ||c [17,24], while all other Mn ions are isotropic Mn 2+ . The three Sm 2 MnMnMn 4−x Ti x O 12 samples have a magnetization direction in the ab plane, perpendicular to the easy axis of the Mn 3+ ions, suggesting that the magnetic anisotropy of Sm 3+ may play an important role despite our data being insensitive to an ordered moment on the Sm1 sites.…”

Origin of negative magnetization phenomena in (Tm1−xMnx)MnDönni1, Pomjakushin2, Zhang3 et al. 2020Phys. Rev. B101100View full textAdd to dashboardCite

“…50% of doping can result in the so-called A-site columnarordered quadruple perovskites with a general composition of A 2 A A B 4 O 12 [19], where a square-planar A site is usually occupied by Cu 2+ , Mn 2+ , and Mn 3+ , and a tetrahedral A site by Mn 2+ . Mn cations at three A , A , and B sites can order at the same time, for example, at T N,Mn = 74 K in TmMn 3 O 6 [20] and at T N,Mn = 76 K in NdMnMnSbO 6 [21], while rareearth cations at the A site usually order at lower temperatures: T N,Tm = 28 K in TmMn 3 O 6 and at T N,Nd = 42 K in NdMnMnSbO 6 . Note that in this subfamily of perovskites, the T N,R /T N,Mn ratio is noticeably higher than that of other subfamilies reported so far, and it can even reach unity.…”