Exchange bias in LaFeO₃ nanoparticles

Abstract

Nanoparticles of antiferromagnetic LaFeO3 were prepared by the sol–gel method. An exchange bias effect has been observed and is attributed to the exchange coupling between the ferromagnetic shell and antiferromagnetic core of the particles. The results provide clear evidence of the presence of spontaneous exchange bias in this system. After field cooling from room temperature, the exchange bias increases while the coercivity decreases with decreasing temperature. Taking into account the role of thermal activation, the temperature dependence of exchange bias and coercivity has been interpreted in terms of the spontaneous exchange bias mechanism proposed recently.

Microwave Combustion Synthesis of Silver Doped Lanthanum Ferrite Magnetic Nanoparticles

“…The coercivity (Hci), retentivity (Mr), and saturation magnetization (Ms) obtained for the samples are given in Table 3. The coercivity (Hci) and saturation magnetization (Ms) observed for lanthanum ferrite is 82.69 G and 4.73emug -1 indicating weak ferromagnetic behavior that arises due to structural distortion related to tilt in FeO 6 octahedra, the results are in agreement with the reported values [23][24][25] . However, predominant mechanism for weak (Parasitic) ferromagnetism in the orthoferrites appears to be anisotropic super exchange (antisymmetric super exchange) 26.…”

Spontaneous exchange bias in a nanocomposite of BiFeO3-Bi2Fe4O9

“…Using a combination of maximum field of loop tracing (H m ) as well as the path followed in tracing the looppositive or negative-it is possible to tune the magnitude of the exchange bias. This tunability, in turn, can increase the functionality in electrically switching the magnetic anisotropy of a ferromagnetic system in a BiFeO 3 -ferromagnetic composite like the present one via multiferroic coupling between ferroelectric polarization and magnetization in BiFeO 3 .…”

“…In recent times, the spontaneous exchange bias (SEB) has been reported for different alloys and nanoparticle composite systems. [1][2][3][4] The origin of this appears to be lying in the biaxiality of AFM grains and variation in the FM-AFM bias coupling among an ensemble of grains. We report here that we have observed an even more interesting feature of the SEBvariation in the magnitude of the bias depending on the path followed in tracing the hysteresis loop-in a nanocomposite of BiFeO 3 -Bi 2 Fe 4 O 9 .…”

Superparamagnetic Behaviour and Induced Ferrimagnetism of LaFeO3 Nanoparticles Prepared by a Hot-Soap Technique

“…The exchange field was linearly increased with increasing the heat-treatment temperature. The exchange bias was generally attributed to the exchange coupling between the ferromagnetic shell and the antiferromagnetic core of the particles [31]. In the case of LaFeO3 particles, the uncompensated surface spins and/or the enhanced spin cantings near the surface region should cause the considerable magnetization.…”