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Slow Spin Relaxation in Dioxocobaltate(II) Anions Embedded in the Lattice of Calcium Hydroxyapatite
Inorganic Chemistry ( IF 4.3 ) Pub Date : 2017-11-07 00:00:00 , DOI: 10.1021/acs.inorgchem.7b02237
Mikhail A. Zykin , Konstantin A. Babeshkin , Oxana V. Magdysyuk 1 , Evgeny O. Anokhin , Walter Schnelle 2 , Claudia Felser 2 , Martin Jansen 2, 3 , Pavel E. Kazin
Affiliation  

Pure-phase cobalt-doped calcium hydroxyapatite ceramic samples with composition Ca10(PO4)6[(CoO2)x(OH)1–2x]2, where x = 0–0.2, were synthesized by high-temperature solid-state reaction, and their crystal structures, vibrational spectra, and magnetic properties were studied. Co atoms are found to enter into the apatite trigonal channel formally substituting H atoms and forming bent dioxocobaltate(II) anions. The anion exhibits single-molecule-magnet (SMM) behavior: slow relaxation of magnetization below 8 K under a nonzero magnetic field with an energy barrier of 63 cm–1. The barrier value does not depend on the concentration of Co ions, virtually coincides with the zero-field-splitting energy as determined from direct-current magnetization, and is very close to the value obtained earlier for cobalt-doped strontium hydroxyapatite. Moreover, the vibration frequencies of the dioxocobaltate(II) anion are found to be the same in calcium and strontium apatite matrixes. The very weak dependence of the SMM parameters on the matrix nature in combination with good chemical and thermal stabilities of the compounds provides wide opportunities to exploit the intrinsic properties of such a SMM-like anion.

中文翻译:

嵌入羟基磷灰石钙晶格中的二氧代钴酸根(II)阴离子的慢自旋弛豫

通过高温固相合成法制备了组成为Ca 10(PO 46 [(CoO 2x(OH)1-2 x ] 2x = 0-0.2 )的纯相钴掺杂羟基磷灰石陶瓷样品。态反应,以及它们的晶体结构,振动光谱和磁性能进行了研究。发现Co原子进入磷灰石三角通道中,正式取代了H原子并形成了弯曲的二氧杂钴酸根(II)阴离子。阴离子表现出单分子磁体(SMM)行为:在非零磁场和63 cm –1的能垒下,磁化作用在8 K以下缓慢弛豫。势垒值不取决于Co离子的浓度,实际上与由直流磁化确定的零场分裂能一致,并且非常接近早先对于钴掺杂的羟基锶磷灰石获得的值。此外,发现钙和锶磷灰石基体中二氧代钴酸根(II)阴离子的振动频率相同。SMM参数对基质性质的非常弱的依赖性以及化合物的良好化学稳定性和热稳定性为利用此类SMM类阴离子的内在特性提供了广泛的机会。
更新日期:2017-11-07
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