Recognition of exchange striction as the origin of magnetoelectric coupling in multiferroics

Pressure-induced commensurate order in TbMn2O5 and DyMn2O5 : Influen

“…It seems that either one or the other mechanism may dominate, depending on the compound or temperature range considered [1,[3][4][5][6][7][8]. The relative roles of such mechanisms in the low-temperature spin order ferroelectricity are actively investigated in the series [9][10][11][12].…”

Experimental evidence for the microscopic mechanism of the unusual spin-induced electric polarization in GdMn2O5

“…In most of the spin induced multiferroics, the Dzyaloshinskii-Moriya interaction between non colinear spins has been proposed as the microscopic mechanism of the magnetic ferroelectricity. However in the case of the RMn 2 O 5 family, the observation of a perfectly colinear spin arrangement along the c axis in SmMn 2 O 5 , has recently definitively ascribed the ferroelectricity to an Mn-Mn exchange-striction model [7]. Gd-Mn symmetric exchange striction, in addition to the Mn-Mn exchange striction mechanism, have recently been suggested in order to explain the large polarization measured in GdMn 2 O 5 [3] but without any proposed microscopic mechanism.…”

“…It is thus the symmetry breaking from P bam to P m which allows the two J 3 interactions to be inequivalent, that is responsible for the observed polarization. Indeed, to release the magnetic frustration, one needs atomic displacements increasing the J 3 super-exchange term between antiferromagnetically ordered moments, and decreasing it between ferromagnetically ordered ones [7]. Following the analysis of reference [10], the main way to modify J 3 is to change the angles α and β in order to maximize the Mn 3+ (t 2g )-O 4 (2p)-Mn 4+ (t 2g ) orbitals' overlap (see Figure 8).…”

Pressure-dependent X-ray diffraction of the multiferroics RMn2O5

“…Unlike many multiferroic compounds, the microscopic origin of the magnetoelectric coupling cannot be attributed to the Dzyaloshinskii-Moriya interaction (Kimura, 2007), which is incompatible with the nearly collinear character of the RMn 2 O 5 spin orders. Instead an 'exchange-striction' mechanism, first proposed by Chapon et al (2006), was recently established (Yahia et al, 2017). In addition, the microscopic mechanism of the atomic displacements responsible for the polarization was unveiled (Yahia et al, 2018).…”