Control of Chiral Magnetism Through Electric Fields in Multiferroic Compounds above the Long-Range Multiferroic Transition

Abstract

Polarized neutron scattering experiments reveal that type-II multiferroics allow for controlling the spin chirality by external electric fields even in the absence of long-range multiferroic order. In the two prototype compounds TbMnO 3 and MnWO 4 , chiral magnetism associated with soft overdamped electromagnons can be observed above the long-range multiferroic transition temperature T MF , and it is possible to control it through an electric field. While MnWO 4 exhibits chiral correlations only in a tiny temperature interval above T MF , in TbMnO 3 chiral magnetism can be observed over several kelvin up to the lock-in transition, which is well separated from T MF . DOI: 10.1103/PhysRevLett.119.177201 Multiferroic materials with coupled magnetic and ferroelectric order bear considerable application potential [1,2]. In type-II multiferroics, magnetic order directly induces ferroelectric polarization and giant magnetoelectric coupling. External magnetic fields imply a flop of electric polarization, and electric fields can control chiral magnetic domains [1][2][3][4][5]. Various neutron experiments [6][7][8][9][10][11][12] as well as resonant and nonresonant x-ray studies [13,14] show that cooling in electric fields enforces a monodomain chiral state, and varying external electric fields at constant temperature drives the chiral magnetic order [9][10][11][12], which corresponds to the most promising application as a data storage medium. In addition, time resolved soft x-ray diffraction showed that chiral magnetism can be manipulated by THz-radiation pulses at an electromagnon energy [15].So far, studies of the multiferroic coupling and hysteresis curves were restricted to the phases with long-range magnetic order on bulk or film materials [16], while only small multiferroic blocks would be vital for applications. Also, from the fundamental point of view, one may ask whether multiferroic hysteresis and control can be achieved in short-range systems above the long-range static multiferroic transition, and how far spin chirality persists above the static and long-range multiferroic order. The mixed system Ni 0.42 Mn 0.58 TiO 3 already indicates that magnetoelectric coupling can persist in cluster systems with competing magnetic structures [17], but until now there has been no information about the control and multiferroic coupling of chiral ordering that is limited in space and time. Here, we study two prototype type-II multiferroics, TbMnO 3 [1, 3,4] and MnWO 4 [18-20], above the long-range ferroelectric transition at zero electric field T MF , where it is still possible to pole and control chiral magnetic correlations. Although the two materials exhibit a similar sequence of magnetic transitions, it turns out that only in TbMnO 3 can chiral scattering be controlled over a large temperature interval of several kelvin.TbMnO 3 (MnWO 4 ) both exhibit a first magnetic transition at T N ¼ 42 K (13.5 K), followed by a second transition at lower temperature, at which cycloid order develops at T MF ¼ 27.6 K (12.6 K). For ...

Chiral Order and Multiferroic Domain Relaxation in NaFeGe$_2$O$_6$

“…The understanding of the read and write performance under different conditions is indispensable for the development of new memory devices. The control and the dynamics of multiferroic domain inversion were studied intensively for TbMnO 3 and MnWO 4 using neutron scattering techniques, second-harmonic generation (SHG) measurements and dielectric spectroscopy [17][18][19][20][21]. The relaxation behavior in both systems differs significantly as a function of temperature and electric-field amplitude [18][19][20].…”

Chiral order and multiferroic domain relaxation in NaFeGe2O6

“…The understanding of the read and write performance under different conditions is indispensable for the development of new memory devices. The control and the dynamics of multiferroic domain inversion were studied intensively for TbMnO 3 and MnWO 4 using neutron scattering techniques, second-harmonic generation (SHG) measurements, and dielectric spectroscopy [17][18][19][20][21]. The relaxation behavior in both systems differs significantly as a function of temperature and electric-field amplitude [18][19][20].…”

The optical tweezer of skyrmions

“…The mechanism of trapping of a skyrmion relies on the interaction between the electric component of the laser field and the ferroelectric polarization of the skyrmion texture. As for the specific materials, we focus on two types of materials: spin-driven single-phase multiferroics and Yttrium Iron Garnet (YIG) [11][12][13][14] . In particular, we present in addition to YIG, results for the multiferroic material Cu 2 OSeO 3 , which supports skyrmions.…”