Scientists found two tricritical points experimentally by critical scaling in Chiral Magnetic Solition system Cr_1/3NbS₂, according to a recent study by a joint team of Prof. ZHANG Lei's Group in High Magnetic Field Laboratory, Chinese Academy of Sciences (CHMFL) and Prof. David G. Mandrus's Group in the University of Tennessee, U.S.A..

Chiral magnetic soliton is a quasi-particle spin-texture with a shape of soliton and it can move, transmit, and form chiral magnetic soliton lattice (CSL) in materials.

Due to the small driven-current compared with that in the traditional microelectronics, chiral magnetic soliton can be manipulated effectively by an external magnetic field or a current injection, making it potentially applicable as a spintronic device.

When an external magnetic field is applied above a threshold value, the helimagnetic (HM) ordering is usually modulated into particle-like spin-textures. With the increase of applied magnetic field, a phase transition from an incommensurate CSL to a commensurate the Polarized Ferromagnetic (FFM) state occurs in Cr_1/3NbS₂.

In this work, researchers investigated the magnetism of the single-crystal Cr_1/3NbS₂.

The M(H) curve with H⊥c displays a loop on the boundary of the phase transition, which suggests that the CSL phase is magnetically metastable.

They obtained critical exponents of Cr_1/3NbS₂, which are close to the theoretical prediction of the 3D-Heisenberg model, and it suggests the short-range magnetic coupling interaction.

Based on the scaling equation, the team constructed the H–T phase diagram around TC, based on which two critical points are determined. The results are consistent with recent theoretical studies.

One critical point is a tricritical one (~310Oe), which locates at the intersection across the CSL, the FFM, and the PM states.

The other critical point is a zero-field critical one (~85Oe), which is situated at the intersection across the CSL, the HM, and the PM states.

These results are meaningful for the understanding of the chiral magnetic state.

This work has been published in Physical Review B entitled Tricritical point and phase diagram based on critical scaling in the monoaxialchiral helimagnet Cr_1/3NbS₂.

This work was supported by the National Key R&D Program of China and the National Natural Science Foundation of China. 

The rescaling plot and H-T phase diagram of Chiral Magnetic Solition of Cr1/3NbS2: Fig.(a) Chiral Magnetic Solition of Cr1/3NbS2; (b)the propagation and movement of the chiral magnetic soliton by the current injection; (c)the rescaling plot of m2 vs h/m; (d)the H -T phase diagram in the vicinity of the phasetransition.