CACTI, Universidade de Vigo, 36310 Vigo, Spain.
Institut de Ciència de Materials de Barcelona (ICMAB-CSIC), Campus de la UAB, 08193 Bellaterra, Spain.
Nano Lett. 2023 Mar 8;23(5):1688-1695. doi: 10.1021/acs.nanolett.2c04268. Epub 2023 Feb 27.
Oxidized cobalt ferrite nanocrystals with a modified distribution of the magnetic cations in their spinel structure give place to an unusual exchange-coupled system with a double reversal of the magnetization, exchange bias, and increased coercivity, but without the presence of a clear physical interface that delimits two well-differentiated magnetic phases. More specifically, the partial oxidation of cobalt cations and the formation of Fe vacancies at the surface region entail the formation of a cobalt-rich mixed ferrite spinel, which is strongly pinned by the ferrimagnetic background from the cobalt ferrite lattice. This particular configuration of exchange-biased magnetic behavior, involving two different magnetic phases but without the occurrence of a crystallographically coherent interface, revolutionizes the established concept of exchange bias phenomenology.
具有尖晶石结构中磁性阳离子分布得到改良的氧化钴铁纳米晶体产生了一种不寻常的交换耦合系统，具有双磁化反转、交换偏置和矫顽力增加，但不存在明确的物理界面来分隔两个截然不同的磁性相。更具体地说，钴阳离子的部分氧化和表面区域中 Fe 空位的形成导致富钴混合铁酸盐尖晶石的形成，该尖晶石被钴铁酸盐晶格的反铁磁背景强烈钉扎。这种涉及两个不同磁性相但没有发生结晶学相干界面的交换偏置磁性行为的特殊配置彻底改变了已建立的交换偏置现象学概念。
