Electric current control of spin helicity in an itinerant helimagnet

Abstract

Chirality is breaking of mirror symmetry in matter. In the fields of biology and chemistry, this is particularly important because some of the essential molecules in life such as amino acids and DNA have chirality. It is a long-standing mystery how one of the enantiomers was chosen at the beginning stage of life 1,2 . The understanding of the emergence of homochirality under some conditions is indispensable for the study of the origin of life as well as pharmaceutical science. The chirality is also emergent in magnetic structures. The longitudinal helical magnetic structure is the chiral object composed of magnetic moments, in which the ordered direction of the magnetic moment spatially rotates in the plane perpendicular to the propagation vector ( Fig. 1a). Since the sense of rotation, which is denoted as helicity, is reversed by any mirror operation, it is corresponding to the chirality.Here we show that the chirality of a longitudinal helical structure can be controlled by the magnetic field and electric current owing to the spin-transfer torque irrelevant to the spin-orbit interaction and probed by electrical magnetochiral effect, which is sensitive to the chiral symmetry breaking, in an itinerant helimagnet MnP. This phenomenon is distinct from the multiferroicity in transversetype insulating helical magnets 3-6 , in which the helical plane is parallel to the propagation vector, because the magnetic structure has polar symmetry not chiral one. While the combination of the magnetic field and electric current satisfies the symmetrical rule of external stimulus for the chirality control 1,2 , the control with them was not reported for any chiral object previously. The present result may pave a new route to the control of chiralities originating from magnetic and atomical arrangements.

Chiral properties of the zero-field spiral state and field-induced magnetic phases of the itinerant kagome metal YMn$_6$Sn$_6$

“…What can result in unequal spin-flip channel populations for centrosymmetric crystals is some external force to pick out a favorable chiral domain. For example, the simultaneous application of a magnetic field and electric current density was shown to control the chirality in MnP via spin transfer torque [30]. The chiral inequality for the YMn 6 Sn 6 sample used in this study was surprising because no such external perturbation was intentionally applied.…”

Magneto‐chiral anisotropy: From fundamentals to perspectives

“…75 Another form of inverse MChA was reported recently, whereby a chiral spin structure was induced in the itinerant helimagnet MnP by passing an electric current parallel to a magnetic field, the handedness of which depended on the relative orientation of current and field. 76…”

Frustration model and spin excitations in the helimagnet FeP

“…The orthorhombic compound FeP (space group P nma) belongs to the group of frustration-driven helimagnets. Unlike the noncentrosymmetric materials that exhibit a chiral (either left-or right-handed) spin-spiral magnetic order of the same handedness in the entire volume due to the antisymmetric spin-orbit-coupling dependent Dzyaloshinskii-Moriya interaction (DMI) [1][2][3][4][5], the frustration-driven helimagnets retain the degeneracy between the left-and right-handed spin spirals [6][7][8][9][10]. In other words, competing exchange interactions between neighboring spins in the crystal lattice of a material set the period of the spin helix but not its handedness.…”