Zero-Field Magnetic Relaxation in Cerous Magnesium Nitrate below 0.2 K

Anderson, A. C.; Robichaux, J. E.

doi:10.1103/physrevb.3.1410

Cited by 24 publications

(9 citation statements)

References 35 publications

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“…5c) is close to the τ hf −1 ∝ T 2 law theoretically expected for this type of process. 36 The slight deviation in the exponent value indicates that in the studied range of temperatures and fields, the MC does not represent a perfect two-level system. 37 The slow relaxation through RPT has been previously reported in isotropic (L = 0) Gd(III) 37,38 complexes but, to our knowledge, never in Mn examples.…”

Section: Magnetic Measurementsmentioning

confidence: 97%

Preparation and properties of a calcium(ii)-based molecular chain decorated with manganese(ii) butterfly-like complexes

et al. 2014

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The room temperature reaction of [Mn2O2(bipy)4](ClO4)3 (bipy = 2,2'-bipyridine) with Ca(CHCl2COO)2 in methanol produced a yellow crystalline material. The X-ray determined structure comprises of a multiple calcium(II) carboxylate bridged chain-like structure which is decorated with [Mn(bipy)2(OH2)](2+) subunits. The redox behaviour for the complex in H2O and MeCN is reported. In the latter solvent the oxidation of the manganese ions appears to be facilitated by the presence of the calcium ions. Magnetic susceptibility and low temperature magnetization measurements show that the Mn moment is isotropic, with g = 1.99(1) and S = 5/2, confirming it is in the 2+ oxidation state. A very weak antiferromagnetic interaction is also detected. Frequency-dependent ac measurements evidence slow magnetic relaxation of the Mn(bipy)2 units. Two relaxation mechanisms are identified: a very slow direct process and a faster one caused by the Resonant Phonon Trapping mechanism. This is the first example of field-induced single ion magnet (SIM) behavior in a mononuclear Mn(II) complex.

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Section: Magnetic Measurementsmentioning

confidence: 97%

Preparation and properties of a calcium(ii)-based molecular chain decorated with manganese(ii) butterfly-like complexes

et al. 2014

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“…On the other hand, dynamic susceptibility measurements indicate the occurrence of slow relaxation of the magnetization in the presence of an applied dc field ( Figure 22a). This behavior was attributed to phonon bottleneck effects, 48 with relaxation times following a τ = aT n dependence, where n = −2. The high temperature data were fitted to the Arrhenius low: ( τ 0 = 2.5(3) × 10 -7 s, U eff = 26(1) K), while the low temperature ones were fitted to a τ = aT n law, with n= -2.15±0.05.…”

Section: Oligonuclear 3d-4f Complexes With Bi-compartmental Ligands Amentioning

confidence: 99%

The exceptionally rich coordination chemistry generated by Schiff-base ligands derived from o-vanillin

2015

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Ortho-vanillin became very popular in coordination chemistry because of its Schiff bases, which generate a rich variety of complexes, ranging from oligonuclear species to coordination polymers. Some of these organic molecules are particularly useful in metallosupramolecular chemistry for assembling homo- and heterometallic helicates. The Schiff bases obtained using aminoalcohols open the door to the synthesis of homo- and heterometallic clusters with various nuclearities and surprising topologies of the metal centers. Several relevant structural types are reviewed. The heterobinuclear 3d-3d' and 3d-4f complexes are valuable building-blocks for the synthesis of heterotrimetallic systems. Beyond the richness of this chemistry, the complexes obtained from o-vanillin-based Schiff ligands show interesting properties: magnetism, luminescence, chirality, catalysis, cytotoxicity, and ferroelectricity. This paper reviews recent data that illustrate a very fertile and dynamic research field in coordination chemistry and materials science.

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“…In cerium magnesium nitrate the direct process for the population or depopulation of the upper spin level by the loss or gain of a phonon of the same energy is thought to be very fast. [89][90][91] The spin-lattice relaxation time in fact is determined by the relaxation of the temperature of the narrow band of phonons "on speaking terms" with the two-level spin systems to the temperature of the Debye spectrum of phonons in the solid. This idea of a "phonon bottleneck" was introduced by Van Vleck 92 and has been discussed by many authors since.…”

Section: Spin-lattice Resistance In a Paramagnetic Salt (Cmn)mentioning

confidence: 99%

“…The dominant scattering mechanisms in powdered CMN at low temperatures should be the crystal surfaces and praseodymium impurities. 91 In the absence of praseodymium impurity scattering, for diffuse scattering at the surface /,h will be approximately equal to the particle radius. The mean free path for scattering by praseodymium impurities has been evaluated by Anderson and Robichaux using a model discussed by Stoneham.…”

Section: Rv/lph = 2200 M 2 Kw -1mentioning

confidence: 99%

Review paper: Heat transfer between liquid helium and solids below 100 mK

Harrison

1979

J Low Temp Phys

147

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The many experimental determinations of heat transfer between liquid helium and solids are reviewed and compared with the existing theories. Generally heat transfer is a complex process at low temperatures, involving parallel heat paths with several resistances in series in each path. The standard theories for the individual resistances are reviewed and as far as possible a definite value of the expected resistance obtained. ddute He m hqutd He, metals m liquid He, metals m dtlute He m hquld 4He, and miscellaneous experiments. Where appropriate, the experimental results have been reevaluated in terms of standard models for heat transfer and presented as resistance versus temperature on diagrams showing the theoretical predictions. Between 20 and lOOmK many measurements show good agreement with acoustic mismatch theory for thermal boundary resistance. Below 20 mK most experiments have been made with finely divided solids (sintered metals or powdered paramagnetic salts); invariably the resistance has been anomalously low, with the metal/3He systems showing RocT -1 and the metal/dilute 3He in * . -3 9He systems showing RocT . The cerium magnesium nitrate/helium experiments have shown a temperatureindependent resistance and sometimes an RecT -~ dependence. These resistances have been attributed to the spin-lattice resistance in cerium magnesium nitrate. Evidence[or heat transfer by magnetic coupling has been reviewed and it is concluded that the positive evidence has other explanations, while the lack of dependence upon helium pressure, 3He phase, and large magnetic fields is strong negative evidence. If the disagreement of experimental results with standard theory is not to be attributed to magnetic coupling, then several theoretical questions remain to be answered; these questions are posed. Basically, at low temperatures the excitations in solids and liquid helium have wavelengths and mean free paths much larger than the size of the finely divided particles or pores between the particles. Thus theories for bulk solids and bulk liquid helium are not appropriate for describing excitations and their interactions at these low temperatures. 467 0022-2291/79/1200-0467503.00/0 ~) 1979 Plenum Publishing Corporation 468 J.P. Harrison

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Zero-Field Magnetic Relaxation in Cerous Magnesium Nitrate below 0.2 K

Cited by 24 publications

References 35 publications

Preparation and properties of a calcium(ii)-based molecular chain decorated with manganese(ii) butterfly-like complexes

Preparation and properties of a calcium(ii)-based molecular chain decorated with manganese(ii) butterfly-like complexes

The exceptionally rich coordination chemistry generated by Schiff-base ligands derived from o-vanillin

Review paper: Heat transfer between liquid helium and solids below 100 mK

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