Finite size effects in antiferromagnetic NiO nanoparticles
Finite size effects in antiferromagnetic NiO nanoparticles
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DOI：
10.1103/physrevlett.79.1393
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发表时间：
1997-08-18
影响因子：
8.6
通讯作者：
Berkowitz, AE
中科院分区：
文献类型：
--
作者：
Kodama, RH;Makhlouf, SA;Berkowitz, AE
反铁磁NiO纳米颗粒表现出异常的磁性，如大矩、矫顽力和高达10 kOe的环移。这种行为很难理解为二亚晶格的反铁磁有序，这是公认的大块NiO。这些纳米粒子的自旋构型的数值模拟得到了8、6或4亚晶格构型，这表明了一种新的有限尺寸效应，即表面自旋配位的减少导致整个粒子的磁顺序发生了根本性的变化。子晶格之间相对较弱的耦合允许自旋在外加场循环时产生多种反转路径，从而导致大的矫顽力和环路位移。
Antiferromagnetic NiO nanoparticles exhibit anomalous magnetic properties, such as large moments, and coercivities and loop shifts of up to 10 kOe. This behavior is difficult to understand in terms of 2-sublattice antiferromagnetic ordering which is accepted for bulk NiO. Numerical modeling of spin configurations in these nanoparticles yields 8-, 6-, or 4-sublattice configurations, indicating a new finite size effect, in which the reduced coordination of surface spins causes a fundamental change in the magnetic order throughout the particle. The relatively weak coupling between the sublattices allows a variety of reversal paths for the spins upon cycling the applied field, resulting in large coercivities and loop shifts.