| 1. |
- Hudl, Matthias, et al.
(författare)
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Investigation of the magnetic phase transition and magnetocaloric properties of the Mn2FeSbO6 ilmenite
- 2013
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Ingår i: Journal of Magnetism and Magnetic Materials. - : Elsevier BV. - 0304-8853 .- 1873-4766. ; 331, s. 193-197
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Tidskriftsartikel (refereegranskat)abstract
- The magnetic phase transition and magnetocaloric properties of both mineral and synthetic melanostibite Mn2FeSbO6 with ilmenite-type structure have been studied. Mn2FeSbO6 orders ferrimagnetically below 270 K and is found to undergo a second-order magnetic phase transition. The associated magnetic entropy change was found to be 1.7 J/kg K for the mineral and 1.8 J/kg K for the synthetic melanostibite for 5 T field change. For the synthetic Mn2FeSbO6 the adiabatic temperature change was estimated from magnetic- and specific heat measurements and amounts to 0.2 K in 1 T field change. Perspectives of the functional properties of Mn2FeSbO6-based materials are discussed.
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| 2. |
- Ivanov, Sergey A., et al.
(författare)
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Crystal structure and antiferromagnetic spin ordering of LnFe(2/3)Mo(1/3)O(3) (Ln = Nd, Pr, Ce, La) perovskites
- 2015
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 91:9
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Tidskriftsartikel (refereegranskat)abstract
- Stoichiometric polycrystalline samples of LnFe(2/3)Mo(1/3)O(3) (Ln = Nd, Pr, Ce, La) have been prepared by solid-state reaction and studied by means of x-ray and neutron powder diffraction as well as Mossbauer spectroscopy and magnetic measurements. All samples were found to be of single phase and to have Pnma symmetry with valence state +3 of Fe and Mo. It is demonstrated that the B-site cations of LnFe(2/3)Mo(1/3)O(3) in accord with LnFeO(3) order in a G-type antiferromagnetic structure with the magnetic moments aligned along the b axis. However, with significantly lower Neel temperatures than their LnFeO(3) parent compounds. The Fe-O-Fe bond lengths and bond angles and thus themagnitude of the antiferromagnetic superexchange interaction are found to systematically change with the ionic radius of Ln such that T-N increases with increasing radius. Only the CeFe2/3Mo1/3O3 compound experiences a low temperature spin reorientation from alignment along the b axis to the a axis.
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| 3. |
- Ivanov, Sergey A., et al.
(författare)
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Perovskite solid solutions La0.75Bi0.25Fe1-xCrxO3 : Preparation, structural, and magnetic properties
- 2017
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Ingår i: Journal of Solid State Chemistry. - : Elsevier. - 0022-4596 .- 1095-726X. ; 254, s. 166-177
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Tidskriftsartikel (refereegranskat)abstract
- Solid solutions of La0.75Bi0.25Fe1−xCrxO3 (x = 0.1, 0.25, 0.5, and 0.75) prepared by conventional solid state reaction have been studied by means of X-ray powder diffraction (XRPD), neutron powder diffraction (NPD) and magnetic measurements. The NPD and XRPD patterns indicate orthorhombic structure (space group Pnma) for all compositions in the whole temperature range investigated (4–900 K). The lattice parameters of La0.75Bi0.25Fe1−xCrxO3 were found to decrease with the Cr content. It was established that the Fe3+ and Cr3+ cations are randomly positioned at the B-site of the perovskite structure.All samples order antiferromagnetically below transition temperatures that decrease with increasing Cr content, from around 700 K for x = 0.1 to about 300 K for x = 0.75. The antiferromagnetic arrangement of the Fe3+/Cr3+ magnetic moments in the B-site is of G-type along the x-axis (Gx mode) with propagation vector k = (0,0,0) for all concentrations of Cr. Effects of the composition on several structural distortion parameters were investigated and an anomalous variation of the octahedral deformation with Cr content was found. Whilst the overall octahedral deformation varies irregularly with increasing Cr content, the octahedral tilting was found to decrease monotoneously.
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| 4. |
- Ivanov, Sergey, et al.
(författare)
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Modification of the structure and magnetic properties of ceramic La2CoMnO6 with Ru doping
- 2018
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Ingår i: Journal of Alloys and Compounds. - : ELSEVIER SCIENCE SA. - 0925-8388 .- 1873-4669. ; 752, s. 420-430
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Tidskriftsartikel (refereegranskat)abstract
- Effects of Ru doping on the structure and magnetic properties of La2CoMn1-xRuxO6 ceramics with different compositions (x = 0, 0.1, 0.2, 0.3, 0.5, 0.75, 1.0) have been investigated using a variety of complementary techniques (X-ray powder diffraction and photoelectron spectroscopy, electron microscopy, and magnetometry). Phase-pure polycrystalline samples were prepared by the conventional solid-state reaction method including high pressure (3000 kg/cm(2) ) treatment of the original mixture of reagents. X-ray diffraction analyses of the samples accompanied with Rietveld refinement suggested a change in the crystal structure upon doping: for 0 <= x <= 0.3 the structure of the samples is predominantly disordered orthorhombic (s.g. Pnma) which transformed to ordered monoclinic (s.g. P2(1)/n) for 0.5 <= x <= 1. This suggests that Ru doping induces (partial) cation order in the B-sublattice. Magnetic measurements indicated a low temperature ferromagnetic phase, and a positive value of the Curie-Weiss temperature (theta cw) was derived for all samples of composition x <= 0.75. However, the Curie temperature (T-c) and theta cw decreased with increasing Ru doping. These changes in Tc upon doping can be correlated to the changes in the nearest neighbor and next nearest neighbor exchange interactions. The sample with x =1 orders antiferromagnetically at approximately 25 K.
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| 5. |
- Ivanov, Sergey, et al.
(författare)
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Temperature-dependent structural and magnetic properties of R2MMnO6 double perovskites (R=Dy, Gd; M=Ni, Co)
- 2018
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Ingår i: Journal of Materials Science: Materials in Electronics. - : Springer Science and Business Media LLC. - 1573-482X .- 0957-4522. ; 29:21, s. 18581-18592
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Tidskriftsartikel (refereegranskat)abstract
- The structural and magnetic properties of the Dy2CoMnO6, Dy2NiMnO6 and Gd2CoMnO6 double perovskites are investigated using X-ray powder diffraction and squid magnetometry. The materials adopt an orthorhombic structure (space ground Pnma) with disordered Co(Ni)/Mn cations, and exhibit ferrimagnetic transitions near T(C)85, 95, and 115K respectively. T-C was found to monotonously depend on the orthorhombic distortion (a-c)/(a+c) of the compounds. The crystal structure of the compounds was investigated as a function of temperature (16-1100K range), evidencing changes in the BO6 octahedron near T-C. The magnetic entropy changes are estimated for comparison of the magnetocaloric properties to those from literature.
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| 6. |
- Mathieu, Roland, et al.
(författare)
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Magnetic order near 270 K in mineral and synthetic Mn2FeSbO6 ilmenite
- 2011
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 98:20, s. 202505-1-202505-3
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Tidskriftsartikel (refereegranskat)abstract
- The structural and magnetic properties of Mn2FeSbO6 single-crystalline mineral and ceramic samples synthesized under thermobaric treatment have been investigated, and compared to theoretical predictions based on first-principles electronic structure calculations. This ilmenite system displays a sharp magnetic transition just below the room temperature related to a ferrimagnetic ordering of the Mn2+ and Fe3+ cations, which makes Mn2FeSbO6 a promising candidate for designing functional magnetic materials.
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| 7. |
- Mathieu, Roland, et al.
(författare)
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Mn2FeSbO6 : A ferrimagnetic ilmenite and an antiferromagnetic perovskite
- 2013
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 87:1, s. 014408-
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Tidskriftsartikel (refereegranskat)abstract
- Due to its polymorphism, Mn2FeSbO6 can be synthesized at high pressures and temperatures as a ferrimagnetic ilmenite or an antiferromagnetic perovskite. The structural phase transformation is discussed in detail, and magnetic structures are proposed for both phases. The high-pressure Mn2FeSbO6 polymorph is a rare example of A(2)B'B '' O-6 perovskite with solely Mn cations on the A site. Fe and Sb cations are ordered on the B sites. Theoretical calculations for the perovskite phase suggest a complex magnetic structure, holding an electronic polarization.
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| 8. |
- Pramanik, P., et al.
(författare)
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Concentration and temperature dependence of the structural, magnetic, and dielectric properties of La2Ni(Mn1-xRux)O6 solid solutions
- 2023
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Ingår i: Journal of Alloys and Compounds. - : Elsevier. - 0925-8388 .- 1873-4669. ; 968
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Tidskriftsartikel (refereegranskat)abstract
- The crystal structure, magnetic ordering, and dielectric characteristics of polycrystalline powder samples of La2NiMn1-xRuxO6 (x = 0.25-0.75) solid solutions have been studied. The X-ray diffraction results were analysed in detail, and reliably show that all compounds have a monoclinic (P2(1)/n) structure with Ni and Mn/Ru ions occupying the 2c and 2d sites, respectively. Magnetic susceptibility measurements reveal a ferromagnetic order for La2NiMn0.75Ru0.25O6 and La2NiMn0.5Ru0.5O6. The ferromagnetic transition temperature decreases from 200 K for La2NiMn0.75Ru0.25O6 to 175 K for La2NiMn0.5Ru0.5O6. Dielectric measurements show large dielectric constants (similar to 10(4)) at room temperature. In addition, the temperature-dependent loss-tangent Tan delta(T) curves reveal relaxation characteristics due to charge transfer between nearest cations.
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| 9. |
- Ritter, C., et al.
(författare)
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Crystallographic phase coexistence, spin-orbital order transitions, and spontaneous spin flop in TmVO3
- 2016
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Ingår i: PHYSICAL REVIEW B. - 2469-9950. ; 93:5
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Tidskriftsartikel (refereegranskat)abstract
- The thermal evolution of structural and magnetic details of the orthovanadate TmVO3, studied in detail by neutron and synchrotron powder diffraction, is reported. Crystallizing in space group Pnma at room temperature, TmVO3 undergoes a first structural phase transition to P2(1)/a at T-OO = 180 K, where a G-type orbital ordered state develops. At T-S = 75 K, a change back to Pnma occurs, and the establishment of C-type orbital order takes place. The V3+ ions order antiferromagnetically with a magnetic propagation vector k = 0 below T-N1 = 105 K, while the Tm3+ sublattice orders at T-N2 = 20K following the same propagation vector. Between T-N1 and T-S, a coexistence of G-type (P2(1)/a) and C-type (Pnma) orbital ordered states exists. The P2(1)/a phase is magnetically separated into two fractions, which adopt a C(x)C(y)0 and G(x)00 coupling, respectively, while the Pnma volume fraction follows a 0G(y)0 magnetic structure. At T-N2, the appearance of the Tm sublattice magnetization (0C(y)0) leads to a spin flop transition of the V sublattice from 0G(y)0 to G(x)00. The results are presented and analyzed in the general context of the series of RVO3 compounds, and they are used to discuss recent magnetization results.
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| 10. |
- Sarkar, Tapati, et al.
(författare)
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Successive phase transitions in the orthovanadate TmVO3
- 2015
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Ingår i: Journal of Physics D. - : IOP Publishing. - 0022-3727 .- 1361-6463. ; 48:34
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Tidskriftsartikel (refereegranskat)abstract
- Synthesis and crystal structure, magnetization and heat capacity measurements of phase pure polycrystalline TmVO3 are reported. TmVO3 was stabilized in the orthorhombic structure by thermal treatment of the precursor TmVO4 in a reducing atmosphere. Magnetization and heat capacity measurements reveal the presence of several successive structural and magnetic phase transitions in this compound. At T = 108 K, the sample undergoes a transition from a paramagnetic state to an antiferromagnetic state, followed by a second transition at 78 K which is related to spin and orbital reorientation. The heat capacity measurements reveal the presence of a third transition in the paramagnetic state (at T = 175 K), which corresponds to a structural phase transition and orbital ordering. At low temperatures (similar to 15 K) and weak fields, there is an anomaly in the magnetization, which may be associated with antiferromagnetic short range ordering of the Tm3+ ions.
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