Magnetic structure of TbMnO studied with spherical neutron polarimetry

Kajimoto, Ryoichi  ; Matsuda, Masaaki; Wakimoto, Shuichi  ; Takeda, Masayasu  ; Kakurai, Kazuhisa; Mitsui, Yukari*; Yoshizawa, Hideki*

TbMnO is a typical example of multiferroic compound, where ferroelectric transition takes place accompanied by spin ordering. Spontaneous ferroelectric polarization appears when the spin structure transforms from a sinusoidal structure into a cycloidal spiral structure below . Interestingly, the amplitude of the spin modulation in the spiral phase is asymmetric, forming an elliptical spiral ordering. Detail of the magnetic structure should be important to understand the mechanism of the ferroelectricity. Accordingly, we have performed spherical neutron polarimetry on a single crystal of TbMnO using CRYOPAD. By analyzing the polarization of the incident and scattered neutron beam, we were able to obtain detailed information about the magnetic structure including the chirarity of the spiral ordering, the ratio of the major axis and the minor axis of the elliptical spiral, and the angle of the axes of the ellipse relative to the crystalline axes.