Reversible photoinduced phase transitions in single crystals of polydiacetylenes

Koshihara, Shin‐ya; Tokura, Y.; Takeda, Kenji; Koda, T.

doi:10.1103/physrevlett.68.1148

Cited by 215 publications

(122 citation statements)

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“…12,13 The global phase transitions in both directions are also believed to be triggered by metal-to-metal charge transfer (CT) excitations, 14 rather than the photogenerated polarons which have been observed in other compounds. 15 The structural parameters and the local electronic configurations of both the LS ground state and HS metastable excited states are well characterized for CoFe-PBA. 1,2,12,13 However, neither the microscopic transition mechanisms nor the effects of Fe-vacancies, water, and alkali metals on these mechanisms are completely understood, despite considerable experimental and theoretical effort.…”

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confidence: 95%

Reversible mechanism for spin crossover in transition-metal cyanides

Kabir

Vliet

2012

Phys. Rev. B

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We report the mechanisms for reversible and repeatable spin transition in a Prussian blue analog crystal, KCo[Fe(CN)6], derived from first-principles calculations. The forward and reverse transitions are initiated by metal-to-metal charge transfer, followed by the d-electron rearrangement at the Co center. Further, these transitions are strongly correlated with bond lengths within the crystal lattice. Both aspects of this spin crossover are in quantitative agreement with experiments. Moreover, we find that the presence of H2O molecules within this Prussian blue analog crystal is not essential to trigger spin transitions in such materials.

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confidence: 95%

Reversible mechanism for spin crossover in transition-metal cyanides

Kabir

Vliet

2012

Phys. Rev. B

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“…The large concentration of Fe vacancies in this crystal, which might otherwise be thought to be a shortcoming of this material, is an essential prerequisite for the reversible transformations. The present model also implies that the photoinduced change must be a cooperative phenomenon [15,[21][22][23], because the structural change of the entire crystal is induced by excitations in a fraction of the crystal. To confirm our model, a systematic experimental study with varying x in K 1−2x Co 1+x Fe(CN) 6 is desired especially.…”

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confidence: 99%

Novel Mechanism of Photoinduced Reversible Phase Transitions in Molecule-Based Magnets

2001

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A novel microscopic mechanism of bi-directional structural changes is proposed for the photoinduced magnetic phase transition in Co-Fe Prussian blue analogues on the basis of ab initio quantum chemical cluster calculations. It is shown that the local potential energies of various spin states of Co are sensitive to the number of nearest neighbor Fe vacancies. As a result, the forward and backward structural changes are most readily initiated by excitation of different local regions by different photons. This mechanism suggests an effective strategy to realize photoinduced reversible phase transitions in a general system consisting of two local components. 78.90.+t,71.35.Lk, Repeatable switching-on and -off of magnetization by external stimuli such as light is one of the most fascinating phenomena with potential applications in next generation's information storage and processing. A bi-directional photo-induced magnetization was first discovered in a cobalt-iron Prussian blue analogue,Illumination of visible light (500 -700 nm) at low temperature induces a bulk magnetization (presumably, ferrimagnetism), which can be eliminated by illumination of near-IR light (∼1300 nm). In spite of various experimental and theoretical efforts [1,2,[4][5][6][7][8], the microscopic mechanism of the reversible magnetization is still not clear. In this Letter we report ab initio quantum chemical cluster calculations for the Co-Fe Prussian blue analogue, unveiling the microscopic mechanism of the bi-directional photo-induced local structural changes that trigger the phase transitions.The crystal of a Prussian blue analogue K 1−2x Co 1+x Fe(CN) 6 is composed of two metallic sites located on vertices of the cubic lattice and each surrounded by six cyano moieties, as shown in Fig. 1. The d-orbitals of transition metals split into t 2g and e g orbitals by the ligand field. In the case of x =0, there are vacancy sites with replacement of CN by H 2 O as shown in Fig. 1(b). Various fascinating phenomena including a room temperature magnet [9], electrochemically tunable magnets [10], transparent and colored magnetic thin films [11], and photo-induced magnetic dipole inversion [12] have been observed in such non-stoichiometric compounds. We will show that this non-stoichiometric aspect is essential for the reversible photo-induced magnetization.The low spin (LS) configuration of the ground nonmagnetic state and the high spin (HS) configuration of the meta-stable magnetic state of K 0.4 Co 1.3 Fe(CN) 6 · 5H 2 O are most likely Co III (dε 6 , S = 0)Fe II (dε 6 , S = 0) and Co II (dε 5 dγ 2 , S = 3/2)Fe III (dε 5 , S = 1/2), respectively [1,2]. These are depicted in Fig.2 as LS0 and HS0 states. Figure 2 schematically represents the most plausible elementary processes in the cycle of the photo-induced structural change. The LH0 and HS0 states are converted to the intermediate states LS1 and HS1, respectively, by photo-induced charge transfer (CT) between iron and cobalt atoms, and then to the final states HS0 and LS0 by intersystem crossing due t...

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“…Multicolor Luminescence from Semiconductor Nanocrystal Composites Tunable in an Electric Field 139 structural change, which is generally termed photochromism, has been observed for many photochromic molecules with photoactive -electron units and thin films of the semiconducting -conjugated polymer (Koshihara et al 1992). The structural change induced by the photoexcitation is considered to be minimal with least steric hindrance but significantly affects the -conjugation length or the electronic structure.…”

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confidence: 99%

Multicolor Luminescence from Semiconductor Nanocrystal Composites Tunable in an Electric Field

Panin¹

2012

Cathodoluminescence

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Reversible photoinduced phase transitions in single crystals of polydiacetylenes

Cited by 215 publications

References 10 publications

Reversible mechanism for spin crossover in transition-metal cyanides

Reversible mechanism for spin crossover in transition-metal cyanides

Novel Mechanism of Photoinduced Reversible Phase Transitions in Molecule-Based Magnets

Multicolor Luminescence from Semiconductor Nanocrystal Composites Tunable in an Electric Field

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