The Magnetic and Crystallographic Properties of MnBi Studied by Neutron Diffraction.

Andresen, Arne F.; Hälg, W.; Fischer, P.; Stoll, E.; Eriksson, G.; Blinc, R.; Paušak, S.; Ehrenberg, L.; Dumanović, J.

doi:10.3891/acta.chem.scand.21-1543

Cited by 121 publications

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“…2, the magnetic moment of the Mn atom shows a small temperature dependence in the range from 10 to 300 K. The magnetic moment per Mn is 3.60 B and 4.18 B at room temperature and 10 K, which is well in agreement with the magnetic measurements on polycrystalline MnBi, 4,8 on single crystals, 15 and with theoretical band calculations. 17,18 The value at room temperature ͑RT͒ is considerably less than that obtained by previous neutron diffraction measurements, 7 where a value of 4.5 B was claimed at RT. Below 200 K, the magnetic moments of Mn deviate gradually from the direction parallel to the c axis and into the direction nearly perpendicular to the c axis at 50 K. A sharp increase of the angle between Mn magnetic moments and the c axis is observed around 90 K. However, the magnetic moment still shows a very small c-axis component at 10 K, i.e., it is not totally in the basal plane.…”

Section: Resultsmentioning

confidence: 38%

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Structure and magnetic properties of the MnBi low temperature phase

Yang

Yelon

James

et al. 2002

Journal of Applied Physics

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High purity MnBi low temperature phase has been prepared and analyzed using magnetic measurements and neutron diffraction. The low-temperature phase of the MnBi alloy has a coercivity μ0iHc of 2.0 T at 400 K, and exhibits a positive temperature coefficient from 0 to at least 400 K. The neutron data refinement indicated that the Mn atom changes its spin direction from c axis above room temperature to nearly perpendicular to the c axis at 50 K. A canted magnetic structure has been observed below 200 K. The anisotropy field increases with increasing temperature which gives rise to a high coercivity at the higher temperatures. The anisotropic bonded magnets have maximum energy products (BH)max of 7.7 and 4.6 MGOe at room temperature and 400 K, respectively.

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Section: Resultsmentioning

confidence: 38%

“…Mn tends to segregate from the MnBi liquid because of the peritectic reaction, and the diffusion of Mn through MnBi is exceedingly slow. [7][8][9] Many efforts have been made to produce single phase MnBi. [7][8][9][10][11][12][13][14][15] At present, no single phase MnBi has been prepared by sintering Mn and Bi powders.…”

Section: Introductionmentioning

confidence: 99%

Structure and magnetic properties of the MnBi low temperature phase

Yang

Yelon

James

et al. 2002

Journal of Applied Physics

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“…The magnetic moment lies in the c-plane below T SR . This spin reorientation was also observed by neutron diffraction [10,11] and nuclear magnetic resonance (NMR) [12] measurements on LTP-MnBi. However, the relation between the magnetic and structural properties has not yet been clarified in detail [10][11][12][13].…”

Section: Introductionmentioning

confidence: 79%

Magnetic and structural phase transitions of MnBi under high magnetic fields

Koyama

Mitsui

Watanabe

2008

Science and Technology of Advanced Materials

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High-field x-ray diffraction and magnetization measurements and differential thermal analysis (DTA) were carried out for polycrystalline MnBi with an NiAs-type hexagonal structure to investigate its magnetic and structural phase transitions. The lattice parameter a rapidly decreases below the spin reorientation temperature T SR (= 90 K) in a zero magnetic field. The parameter c decreases gradually with decreasing temperature and exhibits an anomaly in the vicinity of T SR . By applying a magnetic field of 5 T, the parameter a increases by ∼0.05% when T < T SR and varies smoothly when 8 T 300 K. DTA data show that the magnetic phase transition temperature from the ferromagnetic state to the paramagnetic state increases linearly at a rate of 2 KT −1 with increasing magnetic field up to 14 T.

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“…3. Previously reported neutron diffraction results are limited to powder diffraction [7,9,24]. The single crystal data allow us to not only determine with greater reliability the intrinsic nature of the spin reorientation transition, but also to extract information about the lattice vibrations through analysis of the temperature dependence of the atomic displacement parameters.…”

Section: B Neutron Diffractionmentioning

confidence: 99%

Symmetry-lowering lattice distortion at the spin reorientation in MnBi single crystals

et al. 2014

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Structural and physical properties determined by measurements on large single crystals of the anisotropic ferromagnet MnBi are reported. The findings support the importance of magnetoelastic effects in this material. X-ray diffraction reveals a structural phase transition at the spin reorientation temperature TSR = 90 K. The distortion is driven by magneto-elastic coupling, and upon cooling transforms the structure from hexagonal to orthorhombic. Heat capacity measurements show a thermal anomaly at the crystallographic transition, which is suppressed rapidly by applied magnetic fields. Effects on the transport and anisotropic magnetic properties of the single crystals are also presented. Increasing anisotropy of the atomic displacement parameters for Bi with increasing temperature above TSR is revealed by neutron diffraction measurements. It is likely that this is directly related to the anisotropic thermal expansion in MnBi, which plays a key role in the spin reorientation and magnetocrystalline anisotropy. The identification of the true ground state crystal structure reported here may be important for future experimental and theoretical studies of this permanent magnet material, which have to date been performed and interpreted using only the high temperature structure.

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The Magnetic and Crystallographic Properties of MnBi Studied by Neutron Diffraction.

Cited by 121 publications

References 0 publications

Structure and magnetic properties of the MnBi low temperature phase

Structure and magnetic properties of the MnBi low temperature phase

Magnetic and structural phase transitions of MnBi under high magnetic fields

Symmetry-lowering lattice distortion at the spin reorientation in MnBi single crystals

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