Crystal structure and magnetic properties of Cr_3Te _5O_(13)Cl_3

摘要

A new chromium tellurite oxochloride, Cr_3Te_5O -(13)Cl_3, has been prepared by solid-state reaction and the crystal structure was determined by single crystal X-ray diffraction. The compound crystallizes in the non-centrosymmetric space group P2 _12_12_1 with the unit cell a = 4.90180(10) ?, b = 17.3394(2) ?, c = 17.5405(2) ?, Z = 4, R_1 = 0.0282. The Cr~(3+) ions have octahedral [CrO_6] oxygen coordination, the Te~(4+) ions have one sided [TeO_3] and [TeO_3Cl] coordinations. The [CrO_6] octahedra are edge sharing and form chains extending along [100]. These are connected by corner sharing [TeO_3] and [TeO_3Cl] groups to form layers parallel to (110). The layers are connected by weak interactions in between Te ~(4+) in the layers and Cl- ions located in between. The compound undergoes antiferromagnetic ordering at ～34 K with a Weiss constant of -230 K. Isothermal magnetization measurements reveal a critical field of about 0.25 T above which the magnetization versus field changes from linear to a Brillouin-like saturation behaviour. The frustration ratio amounts to ～6.8 indicative of sizable competing antiferromagnetic spin-exchange interaction. The dielectric constant ε (6 kHz) amounts to ～7.9 and decreases by about 1% on cooling from 50 K to liquid helium temperatures.