Landau theory for spin transition and ordering phenomena in Fe(II) compounds

Chernyshov, Dmitry; Bürgi, Hans‐Beat; Hostettler, Marc; Törnroos, Karl W.

doi:10.1103/physrevb.70.094116

Cited by 75 publications

(107 citation statements)

References 25 publications

Supporting

Mentioning

104

Contrasting

Order By: Relevance

“…Finally, it should be noted that Landau theory has been also applied to the problem of stepped spin transitions and extended to include the possibility of crystallographic symmetry breaking with long-range order of HS and LS sites at the plateau in both the isothermal and isobaric regimes. 59 Although this model is based solely on symmetry-based arguments, it was used to describe rather satisfactorily the symmetry breaking observed in [Fe(2-pic) 3 ]Cl 2 ·EtOH 9 and the increasing width of the thermal hysteresis of general systems, showing first-order transitions have also been discussed by considering the coupling of elastic strain and the order parameter. 60 …”

Section: Discussionmentioning

confidence: 99%

Pressure-induced two-step spin transition with structural symmetry breaking: X-ray diffraction, magnetic, and Raman studies

et al. 2011

View full text Add to dashboard Cite

We have used single-crystal x-ray diffraction, Raman spectroscopy, and magnetometry to investigate the effect of hydrostatic pressures up to 16 kbar on the molecular spin crossover complex [Fe II (bapbpy)(NCS) 2 ]. A stepped first-order transition from the high-spin (HS) to low-spin (LS) phase was observed upon compression of single-crystal samples. The intermediate phase (IP) is stable between 4 and 11 kbar at room temperature. This phase is characterized by supercell reflections and tripling of the c-axis of the unit cell (C2/c) due to the formation of a periodic [HS-LS-LS] structural motif, as seen in the thermal stepped transition. The pressure-temperature phase diagram reveals an anomalous increase of the thermal hysteresis widths with increasing pressure and the stabilization of the IP across the investigated P-T space.

show abstract

Section: Discussionmentioning

confidence: 99%

Pressure-induced two-step spin transition with structural symmetry breaking: X-ray diffraction, magnetic, and Raman studies

et al. 2011

View full text Add to dashboard Cite

show abstract

“…The Landau theory of phase transition and ordering phenomena was applied to the spin transition, discussing the possibility of ordering between HS and LS sites. 27,28 Therefore the crystalline structure of the binuclear complex may be discussed as a set of mononuclear sites related by inversion symmetry, where the population of HS state may differ from site-to-site. One possibility is the loss of translation symmetry ͓Fig.…”

Section: Symmetry Of the Hs-ls Statementioning

confidence: 99%

Wavelength selective light-induced magnetic effects in the binuclear spin crossover compound{[Fe(bt)(NCS)2]2

et al. 2007

View full text Add to dashboard Cite

Using Fourier transform infrared spectroscopy, x-ray diffraction, and magnetic susceptibility measurements under light irradiation, the selective light-induced excited spin state trapping ͑LIESST͒ and the reversible-LIESST effect have been evidenced and studied in depth in the binuclear spin crossover compound ͕͓Fe͑bt͒ ϫ͑NCS͒ 2 ͔ 2 bpym͖. In this system, each magnetic site can switch from low spin ͑LS͒ to high spin ͑HS͒, so that three states exist, namely, the LS-LS, HS-LS, and HS-HS. All these techniques shine a new light on the high phototunability of this system. In addition to the direct photoswitching from the LS-LS to the HS-LS or to the HS-HS state, here we show that photoinduced switching between the excited photoinduced states can be triggered in a reversible way: from HS-LS to HS-HS ͑irradiation around 800 nm͒, or reverse from HS-HS to HS-LS ͑irradiation around 1300 nm͒. The nature of the intermediate HS-LS state during the thermal and light-induced spin state changes is also discussed by comparing the spectroscopic measurements and the structural analysis. The loss of inversion symmetry in the HS-LS molecular state, where the two magnetic Fe sites are no more equivalent, is not accompanied by any long-range ordering of the noncentrosymmetric molecules in the crystal. Therefore the continuous double-step spin conversion corresponds to a double crossover.

show abstract

“…However, situations where this totally symmetrical order parameter is coupled to another one describing a symmetry breaking also exist. This situation can be efficiently analysed in terms of the Landau theory [26].…”

Section: ρ(R)ρ(0)mentioning

confidence: 99%

PIPT from the Beginning to Future

et al. 2012

View full text Add to dashboard Cite

The birth of the field of photoinduced phase transitions was strongly influenced by the conceptual viewpoint expressed by Professor Y. Toyozawa on the condensation of relaxed excitons. Since this first period, twenty years ago, this young field has been expanding rapidly along a diversity of directions. Nowadays, it goes hand in hand with the challenges of today's science: emergence, nonlinearity, coherence, far away from equilibrium, for example. The control of the functionality of a material via photoexcited states poses many new fundamental questions. Some of them will be overviewed: (i) the nature of the control parameters and the nature of the relevant collective variables, especially the order parameters, which characterize the evolution of the system, (ii) the difference between photoinduced transformations under continuous light irradiation and those resulting from an ultrashort laser pulse, (iii) the physical mechanisms of ultrafast photoinduced phase transitions from the formation and proliferation of phototransformed entities to the softening of a collective mode. 78.47.D- Flash-backThis paper is dedicated in memoriam of Professor Yutaka Toyozawa, a founding father of the field of photoinduced phase transitions (PIPT). After the pioneering experimental work of Koshihara on the observation of the photoinduced neutral-to-ionic instability [1], the paper of Prof. Y. Toyozawa, "Condensation of relaxed excitons in static and dynamic phase transitions" [2], is the fingerprint of his inspiring contribution. He brought out some conceptual keys which strongly influenced our research and that of many of our colleagues. In the conclusion of this paper he emphasizes "the usefulness of the global view-point . . . considering the crossover of the excited and the ground electronic states and correlating static and dynamic phase transitions through the motion of (spontaneously or optically) condensed elementary excitations".A second step was the Taniguchi symposium in 1996 "Relaxations of excited states and photoinduced phase transitions" chaired by Prof. Nasu [3]. The aim of this symposium was to discuss the new problem of unconventionally photoactive materials. In these materials the relaxation of optically excited states result in collective motions or drastic structural changes, involving a large number of atoms and electrons. Actually, in a way this symposium was the precursor of the PIPT conferences. The extension of the physics of self-trapped excitons, which Toyozawa has largely contributed to [4], to systems with electron-spin-lattice cooperative interactions was discussed from the viewpoint of both material science and solid state spectroscopy. * corresponding author; e-mail:herve.cailleau@univ-rennes1.frThroughout this first period different theoretical papers were published, developing this approach to establish some backgrounds in the understanding of photoinduced phase transitions [3,5,6]. At the same period, different approaches of photoinduced phase transitions were introduced [7], in particular to t...

show abstract

Landau theory for spin transition and ordering phenomena in Fe(II) compounds

Cited by 75 publications

References 25 publications

Pressure-induced two-step spin transition with structural symmetry breaking: X-ray diffraction, magnetic, and Raman studies

Pressure-induced two-step spin transition with structural symmetry breaking: X-ray diffraction, magnetic, and Raman studies

Wavelength selective light-induced magnetic effects in the binuclear spin crossover compound{[Fe(bt)(NCS)2]2

PIPT from the Beginning to Future

Contact Info

Product

Resources

About