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Magnetismus Poster: Do., 13:00–15:30 D-P230
Neutron TOF diffraction studies of Cr5−xTixTe8
Zhong-Le Huang 1 , Wolfgang Bensch 1 , Winfried Kockelmann 2
1 Institute of Inorganic Chemistry, CAU- Kiel, Germany – 2 Rutherford Appleton Lab-
oratory, ISIS, Chilton, OX11 0QX, UK
The effect of substitution of Cr by Ti in Cr5Te8 has been investigated with respect to
its crystal structure, magnetic properties, and electronic structure [1]. The compounds
Cr5−xTixTe8 (x = 0, 0.5, 1, 1.5, 1.85, 2, 3, 4, 5) were synthesized at elevated temperatures
followed by slow cooling the samples to room temperature. Three structural
modifications are identified from X-ray powder diffraction data: monoclinic, space
group F2/m for Cr5−xTixTe8 (x = 0, 0.5, 1, 1.5, 1.85), trigonal supercell, space group
P-3m1 for Cr5−xTixTe8 (x = 2, 3), and trigonal basic cell, space group P-3m1 for
Cr5−xTixTe8 (x = 4, 5). The structures of all these phases are related to the NiAs
structure with full and deficient metal layers stacking alternatively along the c axis. The
irreversibility in the field-cooled/zero-field-cooled magnetization with low field depends
strongly on the Ti concentration x. Four types of magnetic states are distinguished: reentrant
ferromagnet for m-Cr5Te8, cluster-glass for m-Cr4.5Ti0.5Te8 and m-Cr4TiTe8,
antiferromagnetic for m-Cr3.5Ti1.5Te8, and spin-glass for tr-Cr3Ti2Te8, tr-Cr2Ti3Te8,
and Cr0.25TiTe2. Here we report the neutron TOF studies (OSIRIS/ISIS, Rutherford
Appleton Lab., UK) for m-Cr5Te8, m-Cr4TiTe8, m-Cr3.5Ti1.5Te8, and tr-Cr3Ti2Te8
at temperatures from 1.5 K to temperatures above Tc. For the first two compounds,
both FM and AFM Bragg peaks are observed at low temperatures, indicating the
existence of long-range magnetic order. The set-in temperatures of FM/AFM peaks
are 190/75 and 70/40 K for m-Cr5Te8 and m-Cr4TiTe8, respectively. The magnetic
moments of the FM phase are along the c-axis and those of the AFM phase are found
in the ab-plane. For m-Cr3.5Ti1.5Te8 and Cr3Ti2Te8, no magnetic Bragg scattering
or background modulation were observed down to 1.5 K, indicating short-range magnetic
correlations. The efforts to correlate the structural and magnetic properties and
to understand the origin of the observed bulk magnetism from a microscopic point of
view will be presented.
[1] Zhong-Le Huang, W. Bensch, D. Benea, H. Ebert. J. Solid State Chem. 178
(2005) 2778.