Magnetically induced ferroelectricity inCu2MnSnS4andCu2

Abstract

We investigate magnetically-induced ferroelectricity in Cu2MnSnS4 by means of Landau theory of phase transitions and of ab initio density functional theory. As expected from the Landau approach, ab initio calculations show that a non-zero ferroelectric polarization P along the y direction (of the order of a tenth of µC/cm 2 ) is induced by the peculiar antiferromagnetic configuration of Mn spins occurring in Cu2MnSnS4. The comparison between P , calculated either via density-functionaltheory or according to Landau approach, clearly shows that ferroelectricity is mainly driven by Heisenberg-exchange terms and only to a minor extent by relativistic terms. At variance with previous examples of collinear antiferromagnets with magnetically-induced ferroelectricity (such as AFM-E HoMnO3), the ionic displacements occurring upon magnetic ordering are very small, so that the exchange-striction mechanism (i.e. displacement of ions so as to minimize the magnetic coupling energy) is not effective here. Rather, the microscopic mechanism at the basis of polarization has mostly an electronic origin. In this framework, we propose the small magnetic moment at Cu sites induced by neighboring Mn magnetic moments to play a relevant role in inducing P . Finally, we investigate the effect of the anion by comparing Cu2MnSnSe4 and Cu2MnSnS4: Se-4p states, more delocalized compared to S-3p states, are able to better mediate the Mn-Mn interaction, in turn leading to a higher ferroelectric polarization in the Se-based compound.

Cu2ZnSnS4 Nanorods Doped with Tetrahedral, High Spin Transition Metal Ions: Mn2+, Co2+, and Ni2+

“…9,10,13 The metal ion positions in these structures, their magnetic interactions, and M−M distances, have been characterized and reported in previous magnetism studies. 40 Partially substituting (doping) Cu 2 M x Zn 1−x SnS 4 nanorods (M = Mn 2+ , Co 2+ , Ni 2+ ) with a wurtzite crystal structure (P6 3 mc) could lead to additional and interesting magnetic properties. 16,57 Simple considerations predict that doping and even complete solid solutions are possible over the whole Cu 2 M x Zn 1−x SnS 4 composition range (0 ≤ x ≤ 1).…”

“…36,37 However, in contrast to doped II−VI materials, there are few reports on doping Mn 2+ , Co 2+ , or Ni 2+ into the CZTS lattice. These reports focused mainly on optical properties of the fully (rather than the partially) substituted "CMTS" materials, such as Cu 2 CoSnS 4 , 13−15,38 Cu 2 MnSnS 4 , 39,40 and Cu 2 NiSnS 4 nanocrystals. 16,17,41 Building on the controllable synthesis of colloidal semiconductor nanocrystals, 42−47 we and others recently manipulated the composition and morphology of CZTS nanorods by adjusting the relative reactivity of the molecular precursors used.…”

Large ferroelectric polarization in the new double perovskite NaLaMnWO6 induced by non-polar instabilities

“…Typical multiferroics belong to the group of perovskite transition metal oxides, and include rare-earth manganites and ferrites (e.g. [14][15][16][17][18][19][20][21][22][23][24][25][26][27][28]. In these compounds ferroelectricity is either an independent phenomenon (like in BiFeO 3 ), where ferroelectricity can be caused by an intrinsic polar instability, or its existence is an induced effect of the magnetic ordering (as in TbMnO 3 ), where ferroelectricity is a secondary effect, i.e.…”

First-principles study of ferroelectricity induced by p–d hybridization in ferrimagnetic NiFe 2 O 4

“…In particular, improper multiferroics in which a ferroelectric polarization is induced by electronic correlation effects such as non-centrosymmetric spin, charge, and orbital ordering, is currently under intensive study [9][10][11][12]. This is related to the suggestion that a magneto-electric (ME) coupling in improper multiferroics is expected to be stronger than in proper case, because both dipolar and magnetic orderings share the same physical origin and occur at the same temperature [9].…”

“…Gz, 75.85.+t,Magnetic ferroelectrics that possess ferroelectricity together with some form of magnetic order like ferromagnetic, antiferromagnetic, or ferrimagnetic property in the same crystalline phase have attracted much interest due to their fundamental physics and a great promise for applications in future information technology [2][3][4][5][6][7][8]. In particular, improper multiferroics in which a ferroelectric polarization is induced by electronic correlation effects such as non-centrosymmetric spin, charge, and orbital ordering, is currently under intensive study [9][10][11][12]. This is related to the suggestion that a magneto-electric (ME) coupling in improper multiferroics is expected to be stronger than in proper case, because both dipolar and magnetic orderings share the same physical origin and occur at the same temperature [9].…”