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Co(NH 3 ) 2 Cl 2 and Co(ND 3 ) 2 Cl 2 : Order‐Disorder Behaviour of N(H, D) 3 and Antiferromagnetic Structure
Author(s) -
Leineweber A.,
Jacobs H.,
Eßmann R.,
Allenspach P.,
Fauth F.,
Fischer P.
Publication year - 2001
Publication title -
zeitschrift für anorganische und allgemeine chemie
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.354
H-Index - 66
eISSN - 1521-3749
pISSN - 0044-2313
DOI - 10.1002/1521-3749(200109)627:9<2063::aid-zaac2063>3.0.co;2-t
Subject(s) - antiferromagnetism , octahedron , neutron diffraction , crystallography , paramagnetism , ferromagnetism , crystal structure , order (exchange) , magnetic structure , materials science , powder diffraction , coupling (piping) , chemistry , condensed matter physics , physics , magnetization , magnetic field , metallurgy , quantum mechanics , economics , finance
Diammine cobalt(II) chloride, Co(N(H, D) 3 ) 2 Cl 2 was prepared by decomposition of the corresponding hexaammines at 120 °C in dynamical vacuum. Crystal structures and magnetic properties of these materials were characterised by X‐ray and neutron powder diffraction, and heat capacity measurements. At ambient temperatures Co(N(H, D) 3 ) 2 Cl 2 crystallises in the Cd(NH 3 ) 2 Cl 2 type structure: space group Cmmm , Z = 2, a = 8.0512(2) Å, b = 8.0525(2) Å, c = 3.73318(9) Å (X‐ray data of the H compound). This structure consists of chains of edge‐sharing octahedra $^1_\infty$ [CoCl 4/2 (NH 3 ) 2 ] running along the c ‐axis. Neutron diffraction confirms that that the ND 3 groups are rotationally disordered at ambient temperatures. At 1.5 K and 20 K neutron diffraction data reveal rotational ordering of the ND 3 groups leading to doubling of the c ‐axis and to Ibmm symmetry: a = 7.9999(6) Å, b = 7.9911(5) Å, c = 7.4033(3) Å ( Z = 4, values for T = 1.5 K). Furthermore, antiferromagnetic ordering is present at these temperatures. It is caused by a ferromagnetic coupling of the magnetic moments at Co 2+ (3.60(5) μ B at 1.5 K, 3.22(5) μ B at 20 K) along the octahedra chains $^1_\infty$ [CoCl 4/2 (NH 3 ) 2 ] and antiferromagnetic coupling between neighbouring chains. According to heat capacity measurements the phase transition antiferromagnetic‐paramagnetic takes place at T N = 26 K.