Unusual magnetoelectric effect in paramagnetic rare-earth langasite

Abstract

Violation of time reversal and spatial inversion symmetries has profound consequences for elementary particles and cosmology. Spontaneous breaking of these symmetries at phase transitions gives rise to unconventional physical phenomena in condensed matter systems, such as ferroelectricity induced by magnetic spirals, electromagnons, non-reciprocal propagation of light and spin waves, and the linear magnetoelectric (ME) effect—the electric polarization proportional to the applied magnetic field and the magnetization induced by the electric field. Here, we report the experimental study of the holmium-doped langasite, HoxLa3−xGa5SiO14, showing a puzzling combination of linear and highly non-linear ME responses in the disordered paramagnetic state: its electric polarization grows linearly with the magnetic field but oscillates many times upon rotation of the magnetic field vector. We propose a simple phenomenological Hamiltonian describing this unusual behavior and derive it microscopically using the coupling of magnetic multipoles of the rare-earth ions to the electric field.

Quadratic magnetoelectric effect during field cooling in sputter grown Cr$_2$O$_3$ films

“…We estimate β = −1.69 × 10 −18 s A −1 , based on our previous estimation of microscopic α = 27 × 10 −12 s m −1 [26]. In other multiferroic materials, such as NiSO 4 • 6H 2 O [56] and BiFeO 3 [57], the magnitude of β is comparable to our observation, albeit reported at low temperatures of 3-4 K. Other multiferroics with a non-collinear spin structure have a large quadratic ME effect, observed at very low temperatures and high fields [10,12,[58][59][60]. The microscopic mechanism of the quadratic ME effect in a collinear ferrimagnet requires further investigation.…”

“…The linear ME effect was theoretically predicted and experimentally observed first in the antiferromagnet corundumtype Cr 2 O 3 [2][3][4], and later found a renewed interest in ME-type memories [5][6][7]. Higher-order ME effects that are quadratic in E or H have been found in various materials [8][9][10][11][12]. Equivalent to quadratic ME effects, the linear magneto-optical effect was also found for other antiferromagnets [13].…”

Massive Magnetostriction of the Paramagnetic Insulator KEr(MoO4)2via a Single‐Ion Effect

“…[1][2][3] The fundamental understanding of magnetostrictive effects boosted the technological application of these materials; from magnetic shielding to actuators, rare-earth compounds are widely used. [4][5][6][7] Despite the robust understanding of magnetostriction in ordered rare-earth compounds, [8] and the growing interest toward rare-earth based paramagnetic compounds that show magnetocaloric [9] and magnetoelectric [10] effects, we know much less about the magnetostrictive response of paramagnetic compounds. [11][12][13][14][15][16] In contrast to ferro-and…”

Confirming the trilinear form of the optical magnetoelectric effect in the polar honeycomb antiferromagnet Co$_{2}$Mo$_3$O$_8$

“…The intense research on magnetoelectric and multiferroic compounds in recent years [1][2][3][4][5] has revealed a plethora of novel optical phenomena specific to these materials [2,. Most of these optical effects can be rooted back to the simultaneous breaking of the timereversal and the spatial inversion invariance in these compounds due to their coexisting magnetic and electric orderings [2, 7-23, 25, 26, 30, 33, 34, 37, 38].…”