Giant Coercivity in a One-Dimensional Cobalt-Radical Coordination Magnet

Ishii, Norihiko; Okamura, Yoshitomo; Chiba, Susumu; Nogami, Takashi; Ishida, Takayuki

doi:10.1021/ja077666e

Cited by 270 publications

(151 citation statements)

References 24 publications

(37 reference statements)

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“…Similarly, some mononuclear Co II complexes with N-aryl-N-pyridylaminoxyl ligands of general formula L 4 CoX 2 (NOPy) 4 CoX 2 (X − = NCS − or NCO − ), where a pyridyl nitrogen atom instead of the nitronyl nitroxide unit is coordinated to the metal ion, have shown slow magnetic relaxation [110,111]. Finally, note that the strategy of combining transition metal ions and radicals has also led to systems with higher nuclearity and dimensionality greater than zero, resulting in high spin clusters [112], single-chain magnets [76], and compounds exhibiting long-range magnetic order [113]; however, these compounds are beyond the scope of this review.…”

Section: Nitroxide Radical-containing Complexesmentioning

confidence: 99%

Radical ligand-containing single-molecule magnets

Demir

Jeon

Long

et al. 2015

Coordination Chemistry Reviews

542

386

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Section: Nitroxide Radical-containing Complexesmentioning

confidence: 99%

Radical ligand-containing single-molecule magnets

Demir

Jeon

Long

et al. 2015

Coordination Chemistry Reviews

542

386

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“…[12] As a class of important organic-inorganic hybrid materials, metal phosphonates have potential applications in many fields, including catalysis and separation, [13] photochemistry, [14] magnetism, [15] intercalation chemistry, [16] and biotechnology. [17] Usually, these materials display layered or pillared layered structures where the inorganic layers are separated by organic groups.…”

Section: Mna C H T U N G T R E N N U N G (Tpp)o 2 Phph]·a C H T U N Gmentioning

confidence: 99%

Magnetization Relaxation in a Three‐Dimensional Ligated Cobalt Phosphonate Containing Ferrimagnetic Chains

Wang

Duan

Clemente‐Juan

et al. 2011

Chemistry A European J

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“…These radicals have the unpaired electron essentially delocalized on the two NO groups and are particularly efficient in transmitting the magnetic interaction. They are versatile because their properties can be tuned by changing the substituents attached to the five-membered ring.Recently Ishida and co-workers [9] reported an analogous derivative with a slightly modified NIT-C 6 H 4 -O-R radical in which the original methyl group (1, R = CH 3 ) is substituted by the longer n-butyl group (2, R= (CH 2 ) 3 CH 3 ; Figure 2). In the ferromagnetic chain of Ising spins, the relaxation of the magnetization requires the nucleation of a reversed domain, and it costs four times the nearest-neighbor exchange energy.…”

mentioning

confidence: 99%

“…More intriguing is the very high coercive field of 2. [9] It is not straightforward to compare the results obtained by Ishida and co-workers at low temperature with measurements on traditional hard magnets at room temperature. In fact, an increase of H c at low temperature is also expected for metallic materials; however, it is not as dramatic as the one evidenced by Figure 3.…”

mentioning

confidence: 99%

Record Hard Magnets: Glauber Dynamics Are Key

Sessoli

2008

Angew Chem Int Ed

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chain compounds · cobalt · hysteresis · magnetic properties · radicals Magnetism, and in particular the force that magnetic materials exert at a distance, have fascinated mankind from the beginning of civilization. A material exposed to a magnetic field can retain its magnetized state after the field is removed. The magnetization in this case is cancelled only by applying a field in the opposite direction. The larger the field required to cancel the magnetization, also known as coercive field H c , the harder the magnet. Very hard magnets are important for mechanical devices, and nowadays they are based on intermetallic compounds, mainly SmCo and NdFeB alloys. However, a comparison of hardness based on the coercive field is made difficult by the strong dependence of H c on the preparation process, because the irreversible motion of the domain walls is heavily affected by defects, grain boundaries, and so forth.To date, molecular magnetism has failed to provide materials that at high temperature can compete with metallic hard magnets. Nevertheless, it has played a crucial role in lowdimensional magnetism. In fact, the appropriate choice of building blocks and linkers out of a huge library allows for an efficient confinement of the magnetic interaction. In particular, molecular magnetism has shown that magnetic hysteresis can be observed in the absence of long-range magnetic order in materials in which the magnetic interaction is either restricted to zero dimensions (that is, it has a finite length in three dimensions) or is confined in one dimension. [1] Polynuclear clusters [2] and chains [3] are now being widely investigated for their ability to retain a magnetic memory of purely molecular origin as well as for interesting quantum effects.[4] These two classes of materials have been given the evocative names single molecule magnets, SMM, [5] and single chain magnets, SCM, [6] respectively. For SCM, the possibility to observe the freezing of the magnetization was predicted in the 1960s by Glauber, [7] who developed the kinetic model for a chain of ferromagnetically coupled spins showing Ising-type anisotropy, that is, the spin is confined in one direction and can assume only the up/down configurations. In this case, the hysteresis results from the progressive slowing of the relaxation mechanism as its characteristic time, t, diverges exponentially at low temperature [Eq. (1)]The barrier DE is given by the energy required to nucleate two domain walls, that is, inverting the direction of one spin as shown in Figure 1. This energy is proportional to the intrachain exchange interaction J intra . For the Ising Hamiltonian written as h = JS 2 Ss i s i+1 (where s can only assume the values AE 1, and S is the spin value), the energy difference becomes DE = 4S 2 J intra .The first system to be well rationalized with the Glauber model was a cobalt(II) chain [8] in which the metal ions are linked by nitronyl-nitroxide radicals (Figure 2, top). These radicals have the unpaired electron essentially delocalized on the two NO g...

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Giant Coercivity in a One-Dimensional Cobalt-Radical Coordination Magnet

Abstract: A metal-radical polymer [Co(hfac)2.BPNN] showed a very large coercive field of 52 kOe (4.1 MA m-1) at 6 K, indicating that it is the hardest magnet ever reported. Above 10 K, a soft character appeared, owing to the fast dynamics of magnetization reorientation.

Cited by 270 publications

References 24 publications

Radical ligand-containing single-molecule magnets

Radical ligand-containing single-molecule magnets

Magnetization Relaxation in a Three‐Dimensional Ligated Cobalt Phosphonate Containing Ferrimagnetic Chains

Record Hard Magnets: Glauber Dynamics Are Key

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