Magnetic properties and origins of ferroelectric polarization in multiferroic CaMn7O12

Ferroelectric phase transition and spontaneous electric polarization in CaMn7O12from first principles

“…When the SOC is turned on, the FE polarization of the ground-state R3 phase is 3002 μC m −2 , which is reduced by 7% in comparison with that without SOC. Therefore, our results as well as previous theoretical works [16,17] demonstrate that the giant FE polarization of CaMn 7 O 12 is almost completely determined by the exchange-striction mechanism rather than by the SOC effect.…”

“…A close look at the contributions P z k from different Wyckoff coordinates reveals that each type of ion except O1 has considerable influence, among which the Ca and Mn3 give rise to contributions opposite to the net polarization. In addition, the large counteracting contribution from Ca cations (1516 μC m −2 ) has not been reported in previous theoretical investigations [16,17] and, indeed, it can not be explained by any existing model that takes only account of Mn-O-Mn exchange interactions. It should be pointed out that a similar result has been reported in the TbMnO 3 system although the ferroelectricity is induced by a cycloidal spin spiral via the SOC effect [23,36].…”

“…Based on first-principles calculations, Xiang et al [16] proposed that the microscopic origin of the giant FE polarization in CaMn 7 O 12 is mainly due to the combined effect of the symmetric exchange striction and the antisymmetric Dzyaloshinskii-Moriya (DM) interaction. A subsequent theoretical work [17] confirmed the dominant role of the exchange-striction mechanism, and the spin-dependent p-d hybridization induced by the spin orbital coupling (SOC) also contributes a little polarization.…”

Raman study of phonons inCaMn7O12: Effects of structural modulation and structural transition

“…CaMn 7 O 12 attracts considerable interest due to its complex magnetic structure and observation of strong multiferroic effects [1][2][3][4][5][6]. The high-temperature phase of CaMn 7 O 12 (T > 450 K) is cubic I m3, but below a mixed phase region (400 < T < 450 K), the structure becomes rhombohedral R3 with three nonequivalent Mn sites, occupied by either Mn 3+ or Mn 4+ cations [1].…”

Preparation of Micro-Patterned CaMn7O12 Ceramic Films via a Photosensitive Sol-Gel Method

“…As the second type of single-phase multiferroic material, CaMn 7 O 12 has ferroelectric properties caused by its special helical magnetic structure, and produces a strong magneto-electric coupling effect. Therefore, CaMn 7 O 12 has potential applications in spin electronics, multi-state storage devices, and microelectromechanical system (MEMS) [6][7][8][9][10][11][12]. In recent years, while there have been more studies on the structure and performance of bulk CaMn 7 O 12 (including single crystals and polycrystalline samples), there have been few studies on CaMn 7 O 12 film [13][14][15][16][17][18].…”