Magnetoelectric memory effect of paramagnetic nonpolar phase in Co4Nb2O9

Abstract

A polarization memory effect of the paramagnetic nonpolar phase is observed in magnetoelectric antiferromagnet Co4Nb2O9, which has a magnetic field induced polarization in the antiferromagnetic phase. Following magnetoelectric poling in the polar phase, the nonpolar paramagnetic state retains a strong memory of polarization. When reentering the polar phase without applying the electric field, a polarization along the initial poling direction is recovered. If the applied magnetic field while staying in the paramagnetic phase is weakened, the memory effect is enhanced. With reversing this magnetic field, the polarization is also reversed when reentering the polar phase. The memory effect can be attributed to the ferroelectric seeds forming in the nonpolar phase due to short-range magnetic ordering as evidenced by magnetic entropy data.

Chirality memory stored in magnetic domain walls in the ferromagnetic state of MnP

“…Previously, similar memory effects have been observed in multiferroic helimagnets [18][19][20][21][22][23][24][25]. Some of these effects are suggested to be caused by the so-called polar nanoregion [18][19][20][21]. In other cases, the charge degree of freedom seems to be responsible for the memory effect [22][23][24].…”

“…The origin of this memory effect is ascribed to the Bloch-type domain walls in the ferromagnetic state. Previously, similar memory effects have been observed in multiferroic helimagnets [18][19][20][21][22][23][24][25]. Some of these effects are suggested to be caused by the so-called polar nanoregion [18][19][20][21].…”

Magnetic and structural properties of Ni-substituted magnetoelectric Co4Nb2O9

“…The family of M 4 A 2 O 9 (M = Co, Mn and A = Nb, Tb) compounds was initially reported by Fischer et al [11] to show a similar magnetoelectric coupling under application of a magnetic field below their magnetic ordering temperature. In recent years, several works have been published considering the magnetic, structural, and magnetoelectric features in this series of compounds [9,[12][13][14][15][16][17][18][19][20][21]. Among these compounds, Co 4 Nb 2 O 9 has been reported to show high magnetoelectric coupling at the vicinity of its Néel transition temperature [13,14,17].…”

Symmetry Analysis of Magnetoelectric Effects in Honeycomb Antiferromagnet Co4Nb2O9

“…In the absence of the external magnetic field (H = 0), the magnetic structure is collinear (ϕ = 0) and O 1 = 0 in Eq. (13). Therefore, the polarization does no appear.…”

“…2 Since the reports on a spin-flop driven magneto-dielectric effect 3 and a large magnetoelectric coupling in Co 4 Nb 2 O 9 , 4 this system attracted much attention. [5][6][7][8][9][10][11][12][13] Among them, Khanh and coworkers investigated the linear magnetoelectric effects in detail and found that the electric polarization rotates in the opposite direction at the twice speed relative to the rotation of the external magnetic field applied in the basal ab-plane. 6,9 This point was microscopically studied by Yanagi and coworkers from a band picture under a strong antiferromagnetic (AF) molecular field on the basis of the linear response theory.…”