Praphase concept for the phenomenological description of magnetoelectrics

Sakhnenko, V. P.; Ter-Oganessian, N. V.

doi:10.1134/s1063774511060241

Cited by 13 publications

(28 citation statements)

References 22 publications

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“…This implies the first order character of the PM-AF2 transition. In contrast, earlier based on a phenomenological theory we suggested that similar to MnWO 4 there should exist an intermediate phase between the paramagnetic and ferroelectric phases [20]. We also suggested an orthorhombic praphase for the description of CuO.…”

Section: Cuocontrasting

confidence: 69%

“…We also suggested that the phase transitions in wolframite be described starting from the orthorhombic praphase [19,20]. In this section using the praphase concept and exchange symmetry we discuss the magnetic structures of the magnetic field-induced phases HF, IV, and V and the magnetic field-induced flop of electric polarization (with magnetic field applied along the easy axis).…”

Section: Mnwomentioning

confidence: 99%

“…It was argued that the phase transitions in wolframite can be described using orthorhombic praphase [19,20]. In the monoclinic structure with the monoclinic angle β ≈ 91…”

Section: Mnwomentioning

confidence: 99%

“…Thus, the IR's G 1 and G 2 stem from P 1 , which splits under the action of U xz . Therefore, the magnetically ordered states of MnWO 4 can be interpreted as induced by a single IR P 1 of the orthorhombic praphase [19,20].…”

Section: Hmentioning

confidence: 99%

“…In the case when a commensurate magnetically ordered phase is present in the phase diagram, the order parameters belonging to its wave vector are chosen and the incommensurate phases are found to be well described by the existing Lifshitz invariants. This is, for example, the case of RMn 2 O 5 [15], MnWO 4 [15,19], and CuO [20]. In other cases (such as, for example, in CuCl 2 [21]), when the magnetic order does not lock-in to a commensurate structure, one may choose the commensurate wave vector closest to that of the incommensurate phases to define the order parameters.…”

Section: Introductionmentioning

confidence: 99%

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Interpretation of magnetoelectric phase states using the praphase concept and exchange symmetry

Ter-Oganessian¹,

Sakhnenko²

2013

J. Phys.: Condens. Matter

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Abstract. The majority of magnetoelectric crystals show complex temperaturemagnetic field or temperature-pressure phase diagrams with alternating antiferromagnetic incommensurate, magnetoelectric, and commensurate phases. Such phase diagrams occur as a result of successive magnetic instabilities with respect to different order parameters, which usually transform according to different irreducible representations (IR) of the space group of the crystal. Therefore, in order to build a phenomenological theory of phase transitions in such magnetoelectrics one has to employ several order parameters and assume the proximity of various instabilities on the thermodynamic path. In this work we analyze the magnetoelectrics MnWO 4 , CuO, NaFeSi 2 O 6 , NaFeGe 2 O 6 , Cu 3 Nb 2 O 8 , α-CaCr 2 O 4 , and FeTe 2 O 5 Br using the praphase concept and the symmetry of the exchange Hamiltonian. We find that in all the considered cases the appearing magnetic structures are described by IR's entering into a single exchange multiplet, whereas in the cases of MnWO 4 and CuO by a single IR of the space group of the praphase structure. Therefore, one can interpret the complex phase diagrams of magnetoelectrics as induced by a single IR either of the praphase or of the symmetry group of the exchange Hamiltonian. Detailed temperature-magnetic field phase diagrams of MnWO 4 and CuO for certain field directions are obtained and the magnetic structures of the field-induced phases are determined.

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Section: Cuocontrasting

confidence: 69%

Section: Mnwomentioning

confidence: 99%

“…It was argued that the phase transitions in wolframite can be described using orthorhombic praphase [19,20]. In the monoclinic structure with the monoclinic angle β ≈ 91…”

Section: Mnwomentioning

confidence: 99%

Section: Hmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Interpretation of magnetoelectric phase states using the praphase concept and exchange symmetry

Ter-Oganessian¹,

Sakhnenko²

2013

J. Phys.: Condens. Matter

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Magnetoelectric effect and phase transitions in CuO in external magnetic fields

et al. 2016

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Apart from being so far the only known binary multiferroic compound, CuO has a much higher transition temperature into the multiferroic state, 230 K, than any other known material in which the electric polarization is induced by spontaneous magnetic order, typically lower than 100 K. Although the magnetically induced ferroelectricity of CuO is firmly established, no magnetoelectric effect has been observed so far as direct crosstalk between bulk magnetization and electric polarization counterparts. Here we demonstrate that high magnetic fields of ≈50 T are able to suppress the helical modulation of the spins in the multiferroic phase and dramatically affect the electric polarization. Furthermore, just below the spontaneous transition from commensurate (paraelectric) to incommensurate (ferroelectric) structures at 213 K, even modest magnetic fields induce a transition into the incommensurate structure and then suppress it at higher field. Thus, remarkable hidden magnetoelectric features are uncovered, establishing CuO as prototype multiferroic with abundance of competitive magnetic interactions.

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Induced magnetism and magnetoelectric coupling in ferroelectric BaTiO3 by Cr-doping synthesized by a facile chemical route

2013

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Pure phase barium titanate (BTO) and Cr doped BTO have been synthesized by a facile single step metalorganic decomposition (MOD) method. Thermal gravimetric analysis (TGA) is performed on the processed sample to analyse the thermal stability of the compound. A tetragonal to distorted cubic phase transformation of BTO by Cr doping has been confirmed by X-ray diffraction and Raman spectroscopy. Cr doping in BTO reduced the ferroelectric transition temperature from 122 C to 108 C. A ferroelectric polarization value of 14.5 mC cm À2 for pure BTO was obtained, which decreased to 3.7 mC cm À2 by 1.5 Cr doping. The diamagnetism of BTO partially transformed into ferromagnetic behaviour by Cr-doping at the expense of a decrease in polarization. The magnetoelectric coefficient has been measured by the dynamic ME B method which was recorded as 13 mV cm À1 Oe À1 for 1.5 Cr : BTO at room temperature.Induced electric polarization has been obtained by applying an external magnetic field due to the local interaction of d electron spins with disordered electric dipoles via oxygen vacancies created by the Cr doping in BaTiO 3 . Such materials possess immense potential in low energy consumption for miniaturized device applications in the area of spintronics, sensors and transducers and multistage memory.

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Praphase concept for the phenomenological description of magnetoelectrics

Cited by 13 publications

References 22 publications

Interpretation of magnetoelectric phase states using the praphase concept and exchange symmetry

Interpretation of magnetoelectric phase states using the praphase concept and exchange symmetry

Magnetoelectric effect and phase transitions in CuO in external magnetic fields

Induced magnetism and magnetoelectric coupling in ferroelectric BaTiO3 by Cr-doping synthesized by a facile chemical route

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