Magnetic property of neptunyl (+2) complex NpO $_{2}$ (C $_{6}$ H $_{7}$ O $_{2}$ ) $_{2}$ (C $_{5}$ H $_{5}$ N)

Nakamura, Akio; Nakada, Masami ; Nakamoto, Tadahiro*; Kitazawa, Takafumi*; Takeda, Masuo*

Magnetic property of a nitrogen (N)-coordinated neptunyl (+2) (Np(VI)) complex. 1 NpO $_{2}$ (acac) $_{2}$ (py) (acac=C $_{6}$ H $_{7}$ O $_{2}$ , py=C $_{5}$ H $_{5}$ N) was studied by DC magnetization (M) measurements. While previous $^{237}$ Np Mssbauer data of 1 exhibited para magnetic-relaxation spectra similar to other oxo-neptunyls (+1,+2), the DC- data have revealed many strikingly different features of 1 from the latter: first, its reciprocal susceptibility ( $^{-1}$ ) vs. (K) plots showed a peculiar strongly field ()-dependent nonparamagnetic behavior, which suggests the presence of small ferromagnetic component with $_{C}$ 300 K. In addition, its low-temperature isothermal exhibited anomalous relaxation behavior involving initial over-responsive change and subs equent drift back to its "equilibrium" value ( $_{rm eq}$ ). Moreover, such $_{rm eq}$ showed strong perturbation effect from the SQUID- measurement itself. Such novel magnetic features suggest the presence of a largely metastable fluctuating magnetic (spin plus orbital) state in 1 as a collective body of individual Ising-type neptunyl (O=Np=O) $^{+2}$ molecular magnets.

Language	:	English
Journal	:	Journal of Magnetism and Magnetic Materials
Volume	:	310
Number	:	2, Part2
Pages	:	p.1447 - 1449
Publication Year/Month	:	2007/03
Meeting title	:	17th International Conference on Magnetism (ICM 2006)
Held date	:	2006/08
Location (city)	:	Kyoto
Location (country)	:	Japan
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Keywords	:	no keyword
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Cooperating Institute	:	東邦大学

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Registration No. : BB20061660
JAEA Abstracts No. : 35001168
Paper Submission No. : 2755

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Magnetic property of neptunyl (+2) complex NpO(CHO)(CHN)

Magnetic property of neptunyl (+2) complex NpO $_{2}$ (C $_{6}$ H $_{7}$ O $_{2}$ ) $_{2}$ (C $_{5}$ H $_{5}$ N)