Non-hysteretic colossal magnetoelectricity in a collinear antiferromagnet

Abstract

The manipulation of magnetic ordering with applied electric fields is of pressing interest for new magnetoelectric devices and information storage applications. Recently, such magnetoelectric control was realized in multiferroics. However, their magnetoelectric switching is often accompanied by significant hysteresis, resulting from a large barrier, separating different ferroic states. Hysteresis prevents robust switching, unless the applied field overcomes a certain value (coercive field). Here we address the role of a switching barrier on magnetoelectric control, and identify a material, collinear antiferromagnetic and pyroelectric Ni 3 TeO 6 , in which magnetoelectric switching occurs without hysteresis. The barrier between two magnetic states in the vicinity of a spin-flop transition is almost flat, and thus small changes in external electric/magnetic fields allow to switch the ferroic state through an intermediate state in a continuous manner, resulting in a colossal magnetoelectric response. This colossal magnetoelectric effect resembles the large piezoelectric effect at the morphotropic phase boundary in ferroelectrics.

Tracking the continuous spin-flop transition inNi3TeO6by infrared spectroscopy

“…1 . Reflectance measurements were performed using a series of spectrometers in the ab-plane and along the c-axis between 5 and 300 K. A Kramers-Kronig analysis was used to obtain the optical constants.…”

“…Ni ions have the outer shell electronic configuration t 6 2g e 2 g and spin S = 1, whereas Te is non-magnetic. 1,4 This system thus provides an opportunity to examine (i) magnetoelectric and magnetoelastic coupling when magnetic order develops in a polar lattice and (ii) how transition metal centers mix with non-magnetic ions that have large spin-orbit coupling. The complex magnetism also provides a framework that motivates the search for new high field phases.…”

“…2 Heisenberg exchange striction in this polar material couples spin canting to the polarization change, giving rise to a colossal magnetoelectric effect in the intermediate phase. 1 Considering the foundational role of Heisenberg exchange striction in generating spin-lattice coupling, the complex magnetism, and the enormous field-induced polarization changes, direct measurements of the elementary excitations are important for understanding Ni 3 TeO 6 and other members of this promising family of compounds. [9][10][11][12][13][14][15] Here, we employ infrared vibrational spectroscopy to reveal for the first time the lattice dy- namics of Ni 3 TeO 6 over a broad range of temperature and magnetic field.…”

Successive Magnetic-Field-Induced Transitions and Colossal Magnetoelectric Effect inNi3TeO6

“…The spatial inversion symmetry is broken and the electric polarization points along the c axis, as in Ca 3 ðCo; MnÞO 6 [10,14]. It was found that NTO undergoes a second-order spin-flop (SF) transition at a critical field H c1 ∼9 T, which accompanies a large ME effect [15]. Here, symmetric exchange striction at the SF transition distorts the polar crystal structure to modify the electric polarization.…”

“…The ME coefficient (α ≡ dP=dH) is as high as 1300 ps=m at H c1 , without any magnetic hysteresis. However, a phenomenological model with only two magnetic sublattices was implemented to describe the polarization change at the SF transition [15], whereas a full description of NTO requires a model with six different magnetic sublattices and several competing exchange interactions between them [13].…”