Spin structure of the anisotropic helimagnet Cr1∕3NbS2 in a magnetic field

Abstract

In this letter we describe the ground-state magnetic structure of the highly anisotropic helimagnet Cr 1/3 NbS 2 in a magnetic field. A Heisenberg spin model with Dyzaloshinkii-Moriya interactions and magnetocrystalline anisotropy allows the ground state spin structure to be calculated for magnetic fields of arbitrary strength and direction. Comparison with magnetization measurements shows excellent agreement with the predicted spin structure.Controlling the electrical properties of materials by manipulating their magnetic structure has been one of the primary themes in the field of magnetism research and its applications. Major technological innovations have been based on these efforts, such as giant magnetoresistance in magnetic multilayers systems 1 and magnetic tunneling effects 2 . Recently, non-trivial spin textures, e.g. solitons 3 and skyrmions 4,5 , have received much attention in a similar context 3,6-10 . These objects are especially interesting because of the stability granted by their topology. A detailed understanding of such spin structures, in relation with their effect on electrical properties, is expected to shed light on developing spin-texture based applications 10 . With its layered noncentrosymmetric crystal structure, the helimagnet Cr 1/3 NbS 2 is well-suited for investigations of spin structure, especially toward controlling electrical properties 11,12 . In Cr 1/3 NbS 2 , Cr 3+ ions are intercalated between the hexagonal 2H-NbS 2 layers and magnetically order at T C = 133 K 11,12 . The crystal structure's lack of inversion symmetry, caused by Cr intercalation, results in a helical magnetic ground state oriented along the crystalline c-axis, with spins aligned ferromagnetically within the ab planes. Unlike other well known helimagnets with B20 crystal structure 4,5 , Cr 1/3 NbS 2 only breaks inversion symmetry along the caxis, making it ideal for studying spin-textures in magnetic thin films 13 , which also break inversion symmetry only along the single axis normal to the plane of film.The quasi 2-dimensional (2D) nature of these layered ferromagnetic planes, paired with strong magnetocrystalline anisotropy, allows a clear distinction between the magnetically hard axis (i.e. c-axis of the crystal) and the easy plane (ab-plane). The above qualities of Cr 1/3 NbS 2 greatly resemble those of planar magnetic

Finite-Temperature Properties of Three-Dimensional Chiral Helimagnets

“…The analysis of this model has revealed characteristic magnetization curves, which have been observed in experiments on CrNb 3 S 6 [9,10,[20][21][22] and YbNi 3 Al 9 [13][14][15]. Temperature effect of the spin moment has been included phenomenologically [5,16] and magnetization, entropy and specific heat have been discussed.…”

“…3 are the results calculated by the 2dMC-1dMF method based on Eq. (21). The evaluation of T c (0) is highly improved from the 3dMF description by taking account of the spin-correlation within 2d layers.…”

Incommensurate-commensurate transitions in the monoaxial chiral helimagnet driven by the magnetic field

“…In this work we address the important question of the phase diagram of the monoaxial chiral helimagnet in the magneticfield plane by solving the model without any uncontrolled approximation, and the results obtained are, in some respects, rather different from those in Ref. [15].…”

“…A theoretical attempt has been made recently based on an approximation which makes the model equations easily solvable [15]. As we show in Sec.…”

“…V. A comparison with approximate solutions, namely, the conical approximation of Ref. [15] and the decoupling approximation developed in this work, is presented in Sec. VI, where it is also shown that the form of the phase transition line is universal when the magnitude of the anisotropy is high.…”