X-ray diffraction investigation of a spin crossover hysteresis loop

• Published in: Journal of physics. Condensed matter Vol. 19; no. 32; pp. 326211 - 326211 (11)
• Main Authors: Guionneau, P, Le Gac, F, Lakhoufi, S, Kaiba, A, Chasseau, D, Létard, J-F, Négrier, P, Mondieig, D, Howard, J A K, Léger, J-M
• Format: Journal Article
• Language: English
• Published: Bristol IOP Publishing 15.08.2007; Institute of Physics; IOP Publishing [1989-....]
• Subjects: Chemical Sciences; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Domain effects, magnetization curves, and hysteresis; Exact sciences and technology; Magnetic properties and materials; Magnetically ordered materials: other intrinsic properties; Magnetization curves, magnetization reversal, hysteresis, barkhausen and related effects; Material chemistry; Physics; Spin crossover; Phase transformations; Thiocyanato complex; Magnetic hysteresis; XRD; High temperature; Lattice parameters; Magnetic transitions; Monocrystals; Iron complexes; Domain structure; Temperature effects; Spin crossover; Thermodynamic properties; X-ray diffraction; Iron(II); Hysteresis
• ISSN: 0953-8984; 1361-648X
• DOI: 10.1088/0953-8984/19/32/326211

The nature and the mechanism of the magnetic hysteresis for the thermal spin crossover exhibited by an iron (II) compound is investigated by means of variable-temperature powder and single-crystal x-ray diffraction. The unit cell temperature dependence clearly evidences the amplitude of the strong structural rearrangement that accompanies the spin crossover-corresponding to a variation of 8.6% for one of the unit cell parameters-as well as the structural hysteresis width. In this regard, the present x-ray study reveals significant differences in the spin crossover features according to the nature of the sample-powder or single crystal-that should be taken into account in the analysis of physical properties. Concerning the interplay between structural and magnetic transitions, quenching effects show that the structural transition and the spin crossover are indissociable. Furthermore, investigations of the mechanism itself of the thermal spin crossover confirm the presence of spin-like domains in the conversion region, either in the cooling or in the warming loops. The non-dependence with temperature of these domains inside the hysteresis loop demonstrates the stability of the microscopic and macroscopic structures in the corresponding thermodynamic conditions. This result is of interest in the context of the potential use of hysteresis loops to obtain high-temperature photo-conversion.