Uniaxial-stress enhancement of spin-driven ferroelectric polarization in a multiferroic CuFe1−xGaxO2

We investigate polarization memory effects in single-crystal CuFeO2, which has a magneticallyinduced ferroelectric phase at low temperatures and applied B fields between 7.5 and 13 T. Following electrical poling of the ferroelectric phase, we find that the nonpolar collinear antiferromagnetic ground state at B = 0 T retains a strong memory of the polarization magnitude and direction, such that upon re-entering the ferroelectric phase a net polarization of comparable magnitude to the initial polarization is recovered in the absence of external bias. This memory effect is very robust: in pulsed-magnetic-field measurements, several pulses into the ferroelectric phase with reverse bias are required to switch the polarization direction, with significant switching only seen after the system is driven out of the ferroelectric phase and ground state either magnetically (by application of B > 13 T) or thermally. The memory effect is also largely insensitive to the magnetoelastic domain composition, since no change in the memory effect is observed for a sample driven into a singledomain state by application of stress in the [110] direction. On the basis of Monte Carlo simulations of the ground state spin configurations, we propose that the memory effect is due to the existence of helical domain walls within the nonpolar collinear antiferromagnetic ground state, which would retain the helicity of the polar phase for certain magnetothermal histories.

show abstract

“…It is likely that there will also be some strain enhancement of polarization, as seen in CuFe1−xGaxO2 20 .…”

Section: B Persistent-field Measurementsmentioning

confidence: 99%

Polarization memory in the nonpolar magnetic ground state of multiferroicCuFeO2

et al. 2016

View full text Add to dashboard Cite

show abstract

“…The mechanism used to apply the uniaxial pressure was essentially the same as that of the uniaxial pressure devices used in our previous works. 25,27,28) As shown in Fig. 2(a), a SiCr coil spring, a micrometer, and a loadmeter were attached on top of the cryostat.…”

Section: Methodsmentioning

confidence: 99%

Uniaxial-Pressure Effects on Spin-Driven Lattice Distortions in Geometrically Frustrated Magnets CuFe_1-xGa_xO₂ (x=0, 0.035)

et al. 2013

View full text Add to dashboard Cite

The triangular lattice antiferromagnet CuFeO 2 (CFO) is a spin-lattice coupled system, whose magnetic phase transitions are accompanied by crystal lattice distortions to relieve the geometrical spin frustration. Recent neutron diffraction and magnetic susceptibility measurements on CFO have revealed that the application of uniaxial pressure (up to 100 MPa) in the triangular lattice plane shifts the magnetic phase transition temperatures to higher values [Nakajima et al.: J. Phys. Soc. Jpn. 81 (2012) 094710]. In the present study, we have performed synchrotron radiation x-ray diffraction measurements on CFO and CuFe 1Àx Ga x O 2 (CFGO) with x ¼ 0:035 under applied uniaxial pressure in order to directly observe the uniaxial-pressure effects on the lattice. As a result, we have revealed that the applied uniaxial pressure certainly affects the crystal structure so that the structural transition temperatures increase as well as the magnetic phase transition temperatures. We have also found that CFO exhibits a pronounced lattice instability in the vicinity of the phase transition from the paramagnetic phase with a trigonal structure to an incommensurate magnetic phase with a monoclinic structure. In addition, the present results for CFGO (x ¼ 0:035) have revealed that the lattice instability is suppressed by the substitution of a small amount of nonmagnetic Ga 3þ ions for the magnetic Fe 3þ ions. This indicates that the spin degree of freedom plays an important role in the lattice instability in this system.

show abstract

“…For RbMnBr 3 , a significant decrease in the critical field from the incommensurate to commensurate phases was observed through antiferromagnetic resonance measurements under uniaxial pressure along the direction perpendicular to the hexagonal lattice, and a modification of the periodic variation of the exchange interactions in the lattice was inferred [28]. On the other hand, in the case of CuFeO 2 , an increase in the Néel temperature from the paramagnetic to the incommensurate state, by ∼1.3 K, as well as a change in the volume fraction of the spin-lattice-coupled domains were observed under a uniaxial pressure up to 100 MPa along the direction of the triangular lattice [17,[29][30][31]. These results indicate that the uniaxial pressure breaks the equilateral symmetry of the triangular lattice above the original transition temperature, and partially relieves geometrical spin frustration of a triangular lattice.…”

mentioning

confidence: 99%

“…These studies reveal the significant effect of hydrostatic pressure as regards the modification of exchange interactions in TLAs, however, the controllability of the exchange interaction ratio γ is limited because of the isotropic nature of the hydrostatic pressure. In parallel to these studies, some attempts to anisotropically control the triangular geometry of the spins using uniaxial pressure have been made for single TLA crystals such as RbMnBr 3 [28] and CuFeO 2 [17,[29][30][31]. By changing the uniaxial-pressure direction with respect to the crystal axis, it may be possible to increase, decrease, and tune the ratio of the exchange interactions on a triangular lattice in a controllable way.…”

mentioning

confidence: 99%

“…Despite extensive studies under uniaxial pressure, direct observations that reveal controllability of the exchange interaction ratio still need to be reported. In the present investigation, samples with an optimal size and shape for uniaxial-pressure studies were used, and a maximum uniaxial pressure of 400 MPa was successfully attained using the same pressure cell as that of our previous studies [17,[29][30][31]. This higher uniaxial pressure may enable us to clearly observe a change in the propagation wave vector in CoNb 2 O 6 , which indicates an increase in the nearest-neighbor to next-nearest-neighbor interaction ratio γ from 1.33 to 1.81.…”

mentioning

confidence: 99%

See 1 more Smart Citation

Uniaxial-pressure control of geometrical spin frustration in an Ising antiferromagnetCoNb2O6via anisotropic deformation of the isosceles lattice

et al. 2014

View full text Add to dashboard Cite

We report neutron diffraction measurement results for an Ising antiferromagnet CoNb 2 O 6 under uniaxial pressure along the geometrically frustrated isosceles-triangular-lattice direction. We find that an onset incommensurate wave number at the Néel temperature increases with pressure from 0.378 to 0.411 at 400 MPa. The observations suggest that the anisotropic deformation of the lattice by the uniaxial pressure significantly modifies the spin frustration, leading to an increase in the nearest-neighbor to next-nearest-neighbor interaction ratio from 1.33 to 1.81.Geometrically frustrated triangular-lattice antiferromagnets (TLAs) have been attracting considerable interest because of their diverse phase transitions and critical phenomena [1,2] as well as the recent discovery of multiferroics properties in some TLAs [3][4][5]. For an ideal two-dimensional (2D) triangular lattice with a nearest-neighbor antiferromagnetic interaction, no long-range magnetic order occurs in the case of Ising spins, even at T = 0 K, owing to macroscopic degeneracy of the ground state, whereas a 120 • structure is expected to be stabilized at T = 0 K for Heisenberg or XY-type spins. On the other hand, real TLAs usually exhibit magnetic orders at nonzero temperature, irrespective of spin type, and the phase transition is three dimensional in nature due to the stacking structure of the frustrated triangular lattice. Moreover, there exist other microscopic interactions, such as further-neighbor and dipole-dipole interactions, which reduce the degeneracy of the ground state. Nevertheless, the triangular geometrical frustration does dominate the magnetic order and diverse magnetic features have been experimentally determined in a variety of TLAs [2].A partial releasing of the triangular geometrical frustration due to an orthorhombic distortion also has pronounced effects on magnetic ordering. This distortion splits J on a triangular lattice into two inequivalent antiferromagnetic interactions, J 1 and J 2 , on an isosceles-triangular lattice, as shown in Fig. 1(b). Theoretical investigation of a 2D Ising isosceles-triangular lattice revealed interesting magnetic features, which depend on the interaction ratio, γ = J 1 /J 2 [6-8]. Simple long-range antiferromagnetism is achieved for γ < 1.0 of the triangular lattice, whereas for γ > 1.0 the system only shows a longrange order at T = 0 K, with decoupled chains along the J 1 direction. Above this temperature, magnetic correlations between the chains and an incommensurate magnetic order are seen. The investigation of magnets with geometrically * koba@iwate-u.ac.jp frustrated isosceles-triangular lattices is of great importance, because such a system does not simply belong to the intermediate case between the geometrically frustrated TLA and unfrustrated magnet, but it also has the potential to exhibit unusual magnetic features absent in both magnets.In this Rapid Communication, we report the results of neutron diffraction measurements on an isosceles-triangularlattice Ising antiferromagnet, CoNb ...

show abstract

Uniaxial-stress enhancement of spin-driven ferroelectric polarization in a multiferroic CuFe_1−xGa_xO₂

Cited by 9 publications

References 15 publications

Polarization memory in the nonpolar magnetic ground state of multiferroicCuFeO2

Polarization memory in the nonpolar magnetic ground state of multiferroicCuFeO2

Uniaxial-Pressure Effects on Spin-Driven Lattice Distortions in Geometrically Frustrated Magnets CuFe_1-xGa_xO₂ (x=0, 0.035)

Uniaxial-pressure control of geometrical spin frustration in an Ising antiferromagnetCoNb2O6via anisotropic deformation of the isosceles lattice

Contact Info

Product

Resources

About

Uniaxial-stress enhancement of spin-driven ferroelectric polarization in a multiferroic CuFe1−xGaxO2

Cited by 9 publications

References 15 publications

Polarization memory in the nonpolar magnetic ground state of multiferroicCuFeO2

Polarization memory in the nonpolar magnetic ground state of multiferroicCuFeO2

Uniaxial-Pressure Effects on Spin-Driven Lattice Distortions in Geometrically Frustrated Magnets CuFe1-xGaxO2 (x=0, 0.035)

Uniaxial-pressure control of geometrical spin frustration in an Ising antiferromagnetCoNb2O6via anisotropic deformation of the isosceles lattice

Contact Info

Product

Resources

About

Uniaxial-stress enhancement of spin-driven ferroelectric polarization in a multiferroic CuFe_1−xGa_xO₂

Uniaxial-Pressure Effects on Spin-Driven Lattice Distortions in Geometrically Frustrated Magnets CuFe_1-xGa_xO₂ (x=0, 0.035)