Recipes for enhanced molecular cooling Evangelisti, Marco; Brechin, Euan K
Dalton transactions : an international journal of inorganic chemistry,
01/2010, Letnik:
39, Številka:
2
Journal Article
Recenzirano
Odprti dostop
Molecular nanomagnets are considered valid candidates for magnetic refrigeration at low temperatures. Designing these materials for enhanced cooling requires the control and optimization of the ...quantum properties at the molecular level, in particular: spin ground state, magnetic anisotropy, and presence of low-lying excited spin states. Herein, we present the theoretical framework together with a critical review of recent results, and perspectives for future developments.
Molecular nanomagnets are considered valid candidates for magnetic refrigeration at low temperatures. Herein, we present the theoretical framework together with a critical review of recent results, and perspectives for future developments.
The combination of tripodal alcohols with paramagnetic 3d transition metal ions leads to the isolation of a host of new clusters, high spin molecules and single-molecule magnets ranging in nuclearity ...from two to thirty-two.
Calix[4]arene 3d/4f Magnetic Cooler Karotsis, Georgios; Evangelisti, Marco; Dalgarno, Scott J ...
Angewandte Chemie (International ed.),
December 21, 2009, Letnik:
48, Številka:
52
Journal Article
Recenzirano
Chilling out: The first 3d/4f cluster based on calix4arenes (see picture; purple Mn, brown Gd, red O, blue N) has a high magnetic isotropy and a large number of molecular spin states that are ...populated even at low temperatures, whereas its ferromagnetic limit is approached only at high applied fields. These results enable the complex to be an excellent magnetic refrigerant for low‐temperature applications.
The three‐dimensional metal–organic framework Gd(HCOO)3 is characterized by a relatively compact crystal lattice of weakly interacting Gd3+ spin centers interconnected via lightweight formate ...ligands, overall providing a remarkably large magnetic:non‐magnetic elemental weight ratio. The resulting magnetocaloric effect per unit volume is decidedly superior in Gd(HCOO)3 than in the best known magnetic refrigerant materials for liquid‐helium temperatures and low‐moderate applied fields.
Molecoolers: An unprecedentedly large cryogenic magnetocaloric effect is observed in gadolinium acetate tetrahydrate (see picture, Gd pink, O red, C gray). The change in its magnetic entropy is ...ascribed to the high magnetic density combined with dominant ferromagnetism. For the first time in a molecular complex, direct measurements of the magnetocaloric effect corroborate indirect estimates based on heat capacity and magnetization.
A toroidal magnetic moment in the absence of conventional total magnetic moment is observed in a {Dy6} ring. The reason for the net toroidal arrangement of the local magnetic moments is the high ...symmetry of the complex in combination with strong intra-molecular dipolar interactions between Dy ions. The description of single-ion and inter-ion anisotropic magnetic interactions is achieved here for the first time fully ab initio, i.e., without use of phenomenological parameters.
The magnetothermal properties of a coordination polymer and a metal-organic framework (MOF) based on Gd(3+) ions are reported. An equally large cryogenic magnetocaloric effect (MCE) is found, ...irrespective of the dimensionality. This combined with their robustness makes them appealing for widespread magnetic refrigeration applications.
Magnetic recording using femtosecond laser pulses has recently been achieved in some dielectric media, showing potential for ultrafast data storage applications. Single-molecule magnets (SMMs) are ...metal complexes with two degenerate magnetic ground states and are promising for increasing storage density, but remain unexplored using ultrafast techniques. Here we have explored the dynamics occurring after photoexcitation of a trinuclear µ
-oxo-bridged Mn(III)-based SMM, whose magnetic anisotropy is closely related to the Jahn-Teller distortion. Ultrafast transient absorption spectroscopy in solution reveals oscillations superimposed on the decay traces due to a vibrational wavepacket. Based on complementary measurements and calculations on the monomer Mn(acac)
, we conclude that the wavepacket motion in the trinuclear SMM is constrained along the Jahn-Teller axis due to the µ
-oxo and µ-oxime bridges. Our results provide new possibilities for optical control of the magnetization in SMMs on femtosecond timescales and open up new molecular-design challenges to control the wavepacket motion in the excited state of polynuclear transition-metal complexes.
Structural distortion in a Mn6 complex switches the magnetic exchange from antiferro- to ferromagnetic, resulting in a single-molecule magnet with a record anisotropy barrier.
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