2020同步年報

Neutron Science 077 Fig. 1 : (a) Left axis shows ZFC and FC M(T) curves of Mn 1.5 Cr 1.5 O 4 under applied magnetic field 250 Oe. The right axis represents an inverse magnetic- susceptibility curve. (b) Magnetic order parameter of Mn 1.5 Cr 1.5 O 4 manifested by the integrated intensity of signal (1 1 1). Rietveld plot of Mn 1.5 Cr 1.5 O 4 neutron powder-diffraction (NPD) data at (c) 65 K and (d) 3.5 K. [Reproduced from Ref. 1] Fig. 2 : (a) Small-angle view of the 2D plot of the temperature-dependent diffraction pattern around the (111) signal shows that the back- ground intensity diffuses below 170 K and then concentrates around the (111) signal below T N . (b) Residual magnetic signal obtained from the difference of diffraction patterns at 163 K and 63 K. [Reproduced from Ref. 1] signals above the ordering temperature are generally regarded as the precursor of long-range magnetic order; the inverse signal width reflects the magnetic correlation length or the size of the magnetic clusters. Chou and his coworkers demonstrated the oscillatory nature of the mag- netic diffuse-scattering intensities in Mn 1.5 Cr 1.5 O 4 , which could lead to various physical pictures. The ferromagnetic magnetic correlation above T N could refer to the Griffiths phase; the local minimum in the oscillation might refer to a pinch point in the context of spin ice. This work has indeed triggered a motivation to grow single-crystal samples and to expand the neutron-scattering investigations of spinel compounds. (Reported by Chin-Wei Wang) This report features the work of Hsiung Chou and his collab- orators published in Appl. Phys. Lett. 116 , 182406 (2020). ANSTO WOMBAT – High-intensity Powder Diffractometer ANSTO ECHIDNA – High-resolution Powder Diffractometer • NPD • Condensed-matter Physics References 1. G. D. Dwivedi, C. W. Wang, S. M. Kumawat, H. Chou, Appl. Phys. Lett. 116 , 182406 (2020). 2. C. G. Shull, J. S. Smart, Phys. Rev. 76 , 1256 (1949).