Ferroelectricity and magnetic orderings in Delafossite family compounds

Since discovery of the ferroelectric polarization induced by magnetic field in CuFeO2, delafossite family compounds have attracted much attention, because some theoretical formula, which had been presented, could not explain the ferroelectric polarization of CuFeO2. We have been investigating correlation among their magnetic orderings, lattice symmetry and ferroelectric polarization in AFeO2 (A=Cu, Ag, Na) systems. In CuFeO2, the ferroelectric polarization is induced by chemical substitutions for Fe sites in CuFe1-xBxO2 (B=Al, Ga, Rh, Mn) as well as magnetic field. The magnetic structure in the ferroelectric phase is proper screw type with magnetic point group 21' determined by the neutron diffraction experiments.[1] The ferroelectric polarization parallel to the propagation vector in CuFeO2 can be explained by both extended inverse-Dzyaloshinsky-Moriya(DM) effect and d-p hybridization mechanism. We have also demonstrated that the spin-orbit interaction in Fe ions, coupling spin and orbital orders, plays a crucial role to the ferroelectricity in both of which break the crystal symmetry, by observing incommensurate 2q orbital modulation in the ferroelectric phase of CuFe1-xGaO2 by soft X-ray resonant diffraction.[2] When nonmagnetic Cu ions on A-site are substituted by Ag or Na ions, the magnetic orderings are completely modified from CuFeO2. In AgFeO2, cycloid type magnetic structure with m1' point group is stabilized, which is concomitant with ferroelectric polarization, as the lowest temperature phase in zero-field.[3] Also in alpha-NaFeO2, the other type of cycloidal ordering (m1') appears mainly in magnetic field. In these systems, taking account of extended inverse DM effect, ferroelectric polarization direction is along general direction in the ac plane and does not follow the well-known inverse DM formula. In this presentation, I will discuss the relationship between the magnetic ordering and ferroelectricity in these delafossite family compounds.

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Axial point groups: rank 1, 2, 3 and 4 property tensor tables

Acta Crystallographica Section A Foundations and Advances ◽

10.1107/s2053273315002740 ◽

2015 ◽

Vol 71 (3) ◽

pp. 346-349

Author(s):

Daniel B. Litvin

Keyword(s):

Magnetic Field ◽

Magnetic Structure ◽

Infinite Series ◽

Point Group ◽

Physical Property ◽

Induced Polarization ◽

One Dimensional ◽

Point Groups

The form of a physical property tensor of a quasi-one-dimensional material such as a nanotube or a polymer is determined from the material's axial point group. Tables of the form of rank 1, 2, 3 and 4 property tensors are presented for a wide variety of magnetic and non-magnetic tensor types invariant under each point group in all 31 infinite series of axial point groups. An application of these tables is given in the prediction of the net polarization and magnetic-field-induced polarization in a one-dimensional longitudinal conical magnetic structure in multiferroic hexaferrites.

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The Effect of a Weak Static Magnetic Field in the Range of Magnitudes from a “Zero” Field (0.01 μT) to 100 μT on the Production of Reactive Oxygen Species in Nonactivated Neutrophils

BIOPHYSICS ◽

10.1134/s0006350920030161 ◽

2020 ◽

Vol 65 (3) ◽

pp. 443-447

Author(s):

V. V. Novikov ◽

E. V. Yablokova ◽

I. A. Shaev ◽

E. E. Fesenko

Keyword(s):

Magnetic Field ◽

Reactive Oxygen Species ◽

Static Magnetic Field ◽

Reactive Oxygen ◽

Zero Field ◽

Oxygen Species

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The Location of Magnetic Reconnection at Earth’s Magnetopause

Space Science Reviews ◽

10.1007/s11214-021-00817-8 ◽

2021 ◽

Vol 217 (3) ◽

Author(s):

K. J. Trattner ◽

S. M. Petrinec ◽

S. A. Fuselier

Keyword(s):

Magnetic Field ◽

Solar Wind ◽

Magnetic Reconnection ◽

Ion Beams ◽

Review Article ◽

Observational Evidence ◽

Magnetic Shear ◽

General Direction ◽

Shear Model ◽

Wide Range

AbstractOne of the major questions about magnetic reconnection is how specific solar wind and interplanetary magnetic field conditions influence where reconnection occurs at the Earth’s magnetopause. There are two reconnection scenarios discussed in the literature: a) anti-parallel reconnection and b) component reconnection. Early spacecraft observations were limited to the detection of accelerated ion beams in the magnetopause boundary layer to determine the general direction of the reconnection X-line location with respect to the spacecraft. An improved view of the reconnection location at the magnetopause evolved from ionospheric emissions observed by polar-orbiting imagers. These observations and the observations of accelerated ion beams revealed that both scenarios occur at the magnetopause. Improved methodology using the time-of-flight effect of precipitating ions in the cusp regions and the cutoff velocity of the precipitating and mirroring ion populations was used to pinpoint magnetopause reconnection locations for a wide range of solar wind conditions. The results from these methodologies have been used to construct an empirical reconnection X-line model known as the Maximum Magnetic Shear model. Since this model’s inception, several tests have confirmed its validity and have resulted in modifications to the model for certain solar wind conditions. This review article summarizes the observational evidence for the location of magnetic reconnection at the Earth’s magnetopause, emphasizing the properties and efficacy of the Maximum Magnetic Shear Model.

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Ground state and stability of the fractional plateau phase in metallic Shastry–Sutherland system TmB4

Scientific Reports ◽

10.1038/s41598-021-86353-5 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Matúš Orendáč ◽

Slavomír Gabáni ◽

Pavol Farkašovský ◽

Emil Gažo ◽

Jozef Kačmarčík ◽

...

Keyword(s):

Magnetic Field ◽

Phase Diagram ◽

Ground State ◽

Constant Magnetic Field ◽

Paramagnetic Phase ◽

The Other ◽

Zero Field ◽

Plateau Phase ◽

Low Field ◽

Zero Field Cooling

AbstractWe present a study of the ground state and stability of the fractional plateau phase (FPP) with M/Msat = 1/8 in the metallic Shastry–Sutherland system TmB4. Magnetization (M) measurements show that the FPP states are thermodynamically stable when the sample is cooled in constant magnetic field from the paramagnetic phase to the ordered one at 2 K. On the other hand, after zero-field cooling and subsequent magnetization these states appear to be of dynamic origin. In this case the FPP states are closely associated with the half plateau phase (HPP, M/Msat = ½), mediate the HPP to the low-field antiferromagnetic (AF) phase and depend on the thermodynamic history. Thus, in the same place of the phase diagram both, the stable and the metastable (dynamic) fractional plateau (FP) states, can be observed, depending on the way they are reached. In case of metastable FP states thermodynamic paths are identified that lead to very flat fractional plateaus in the FPP. Moreover, with a further decrease of magnetic field also the low-field AF phase becomes influenced and exhibits a plateau of the order of 1/1000 Msat.

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MICROWAVE ABSORPTION STUDIES ON HIGH-Tc SUPERCONDUCTORS AND RELATED MATERIALS II: Electron Spin Resonance of DPPH Coated on Y1Ba2Cu3Oy as A Probe of Magnetic Field Variations

Modern Physics Letters B ◽

10.1142/s0217984991000964 ◽

1991 ◽

Vol 05 (11) ◽

pp. 779-787

Author(s):

K. SUGAWARA ◽

D.J. BAAR ◽

Y. SHIOHARA ◽

S. TANAKA

Keyword(s):

Magnetic Field ◽

Temporal Variations ◽

Zero Field ◽

High Tc ◽

Spin Resonance ◽

Absorption Studies ◽

Powder Particles ◽

Increasing Temperature ◽

Linewidth Broadening ◽

Magnetic Field Variations

The ESR linewidth (∆H pp ) of DPPH coated on the surface of powder specimens of Y 1 Ba 2 Cu 3 O y has been studied under various magnetic field and temperature conditions. ∆H pp increases substantially with decreasing temperature in the field cooled case, whereas almost no linewidth broadening was found in the zero field cooled case. ∆H pp was found to be sensitive to the applied magnetic field. This effect was very pronounced at temperatures lower than 40 K, but decreased strongly with increasing temperature. The broadening of the resonance lineshape has been attributed to spatial and temporal variations of the fluxon distribution in the powder particles.

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Influence of magnetic field on the paraelectric to ferroelectric phase transition in BaTiO3

Physics Letters A ◽

10.1016/0375-9601(81)90158-4 ◽

1981 ◽

Vol 83 (7) ◽

pp. 347-350 ◽

Cited By ~ 35

Author(s):

D. Wagner ◽

D. Bäuerle

Keyword(s):

Magnetic Field ◽

Phase Transition ◽

Ferroelectric Phase Transition ◽

Ferroelectric Phase

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Reversibility of the Magnetocaloric Effect in the Bean-Rodbell Model

Magnetochemistry ◽

10.3390/magnetochemistry7050060 ◽

2021 ◽

Vol 7 (5) ◽

pp. 60

Author(s):

Luis M. Moreno-Ramírez ◽

Victorino Franco

Keyword(s):

Magnetic Field ◽

Thermal Hysteresis ◽

Entropy Change ◽

Second Order ◽

Zero Field ◽

First Order ◽

Magnetic Field Change ◽

Magnetocaloric Materials ◽

Moderate Magnetic Field ◽

The Magnetic Field

The applicability of magnetocaloric materials is limited by irreversibility. In this work, we evaluate the reversible magnetocaloric response associated with magnetoelastic transitions in the framework of the Bean-Rodbell model. This model allows the description of both second- and first-order magnetoelastic transitions by the modification of the η parameter (η<1 for second-order and η>1 for first-order ones). The response is quantified via the Temperature-averaged Entropy Change (TEC), which has been shown to be an easy and effective figure of merit for magnetocaloric materials. A strong magnetic field dependence of TEC is found for first-order transitions, having a significant increase when the magnetic field is large enough to overcome the thermal hysteresis of the material observed at zero field. This field value, as well as the magnetic field evolution of the transition temperature, strongly depend on the atomic magnetic moment of the material. For a moderate magnetic field change of 2 T, first-order transitions with η≈1.3−1.8 have better TEC than those corresponding to stronger first-order transitions and even second-order ones.

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Magnetic Field versus Temperature Phase Diagram of the Spin-1/2 Alternating-Bond Chain Compound F5PNN

Journal of the Physical Society of Japan ◽

10.1143/jpsj.78.074716 ◽

2009 ◽

Vol 78 (7) ◽

pp. 074716 ◽

Cited By ~ 6

Author(s):

Yasuo Yoshida ◽

Tatsuya Kawae ◽

Yuko Hosokoshi ◽

Katsuya Inoue ◽

Nobuya Maeshima ◽

...

Keyword(s):

Magnetic Field ◽

Phase Diagram ◽

Temperature Phase ◽

Field Versus ◽

Bond Chain ◽

Temperature Phase Diagram ◽

Chain Compound

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Slow magnetisation relaxation in tetraoxolene-bridged rare earth complexes

Dalton Transactions ◽

10.1039/c7dt02932b ◽

2017 ◽

Vol 46 (40) ◽

pp. 13756-13767 ◽

Cited By ~ 16

Author(s):

Maja A. Dunstan ◽

Elodie Rousset ◽

Marie-Emmanuelle Boulon ◽

Robert W. Gable ◽

Lorenzo Sorace ◽

...

Keyword(s):

Magnetic Field ◽

Magnetic Susceptibility ◽

Rare Earth ◽

Slow Relaxation ◽

Rare Earth Complexes ◽

Zero Field ◽

Ac Magnetic Susceptibility ◽

Quantum Tunnelling ◽

Dc Magnetic Field

Two tetraoxolene-bridged dinuclear Dy(iii) complexes exhibit slow relaxation in ac magnetic susceptibility studies with zero-field quantum tunnelling of the magnetisation that is suppressed by the application of a dc magnetic field.

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