Dynamic response of the spin-crossover solid Co(H-2(fsa)2 en)(py)(2) to a pulsed magnetic field

Azzedine Bousseksou (1) , K. Boukheddaden (2) , Michel Goiran (3) , C. Consejo (1, 3) , M.L. Boillot (4) , Jean-Pierre Tuchagues (1)

1 LCC - Laboratoire de chimie de coordination
2 LMOV - Laboratoire de magnétisme et d'optique de Versailles
3 LNCMP - Laboratoire National des Champs Magnétiques Pulsés
4 ICMMO - Institut de Chimie Moléculaire et des Matériaux d'Orsay

The spin transition between the paramagnetic high-spin (HS) and low-spin (LS) electronic states of CoII(H2(fsa)2en)(py)2, [H2(fsa)2en=N,N′-ethylene bis(3-carboxysalicylaldimine), py=pyridine] under a pulsed and intense magnetic field (32 T) has been probed by optical reflectivity. In the absence of perturbation, a thermal hysteresis loop (ΔT=19.4K,T1/2=126K) was detected. Applying a magnetic field of 32 T to the solid, the initial state of which belongs to the ascending branch of the hysteresis loop, leads to an irreversible and quasicomplete S=1/→2S=3/2 transition. The experimental evidence of this crossover triggered by a pulsed magnetic field is reported here in conjunction with an adequate Ising-like model. This two-level model, used as a first approach, allows us to reproduce quantitatively the -4.9 K shift in transition temperature under the effect of the 32 T static magnetic field. The dynamic aspects of the previous model are also explored, leading to a description of the main features of the phenomenon. Indeed, an irreversible (reversible) jump of the high-spin fraction is predicted when the pulsed magnetic field is applied in the metastable LS (HS) phase.

Domaines: Supraconductivité [cond-mat.supr-con]

Azzedine Bousseksou, K. Boukheddaden, Michel Goiran, C. Consejo, M.L. Boillot, et al.. Dynamic response of the spin-crossover solid Co(H-2(fsa)2 en)(py)(2) to a pulsed magnetic field. Physical Review B, 2002, 65, pp.172412. ⟨10.1103/PhysRevB.65.172412⟩. ⟨hal-00015706⟩