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首页> 外文会议>NATO Advanced Research Workshop on Supermaterials Sep 19-23, 1999, Hyeres, France >MAGNETIZATION IN HIGH MAGNETIC FIELD AND CRITICAL MAGNETIC BEHAVIOUR IN NANOSTRUCTURED MAGNETIC OXIDES
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MAGNETIZATION IN HIGH MAGNETIC FIELD AND CRITICAL MAGNETIC BEHAVIOUR IN NANOSTRUCTURED MAGNETIC OXIDES

机译：纳米结构的氧化物中的高磁场磁化和临界磁行为

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The open hysteresis curve up to 140 kOe of nanosized Cu-ferrite particles belong to the area of the paraprocesses, i. e. when the technical saturation is completed and noncollinear orientation in the directions of the magnetic moments appears under the influence of an external magnetic field. At temperatures near the absolute zero, the freezing of non-compensated magnetic moments at the particle surface play an important role for the magnetic losses, while at higher temperatures these losses are probably related to the exchange interactions and paraprocesses in the magnetic sublattices of the ferrite. The paraprocesses of the ferrimagnetic oxides are determined by the length of superexchange interactions of the magnetic ions through the oxygen and are different from the exchange interactions in the metals or spin-glasses. If in the ferrioxide crystalline unit cell there exist local distortions of the sublattices or inter-, intralattices exchange interactions, a large number of disoriented thermal spin movements can be present. In the case of a cooperative JT effect, a low effective exchange field H_(eff) acts, whose direction coincides with that of the external magnetic field. At higher magnetic fields, and up to some critical temperature, the possibility to reach a stable state of the system with parallel magnetic moments between the A and B sublattices appears as a result of the induced noncollinearity in one of the sublattices - this a temperature-dependant process. We believe that up to some critical grain-size in this case both sublattices interact as independent phases with different magnetic orientation and the exchange interactions between these phases depend on the temperature.
机译：高达140 kOe的纳米级铜铁氧体颗粒的开放磁滞曲线属于副过程的区域，即。 e。当技术饱和完成时，在外部磁场的影响下，在磁矩方向上出现了非共线取向。在接近绝对零的温度下，颗粒表面未补偿磁矩的冻结对于磁损耗起着重要作用，而在较高温度下，这些损耗可能与铁氧体磁子晶格中的交换相互作用和副过程有关。亚铁磁性氧化物的副过程取决于通过氧的磁性离子的超交换相互作用的长度，并且不同于金属或自旋玻璃中的交换相互作用。如果在亚铁氧化物晶体晶胞中存在亚晶格的局部变形或晶格间，晶格内的交换相互作用，则可能会出现大量无方向性的热自旋运动。在协同JT效应的情况下，会产生一个低有效的交换磁场H_（eff），其方向与外部磁场的方向一致。在较高的磁场下以及达到一定的临界温度时，由于其中一个子晶格引起了非共线性，因此出现了在A和B子晶格之间具有平行磁矩的系统达到稳定状态的可能性。依赖过程。我们认为，在这种情况下，直到某些临界晶粒尺寸，两个子晶格都作为具有不同磁取向的独立相相互作用，并且这些相之间的交换相互作用取决于温度。

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