Manipulation Of Ferromagnetism Research Articles

QUANTUM MONTE CARLO STUDY OF MAGNETIC CORRELATION IN GRAPHENE NANORIBBONS AND QUANTUM DOTS

To realize the application of spintronics, possible magnetism in graphene-based material is an important issue to be addressed. At the tight banding level of armchair graphene nanoribbons, there are two flat bands in the band structure, two Van Hove singularities in the density of states, and the introducing of the next-nearest-neighbor hopping term cause high asymmetry in them, which plays a key role in the behavior of magnetic correlation. We further our studies within determinant quantum Monte Carlo simulation to treat the electron–electron interaction. It is found that the armchair graphene nanoribbons show carrier mediated magnetic correlation. In the armchair graphene nanoribbons, the antiferromagnetic correlation dominates around half filling, while the ferromagnetic correlation dominates as electron filling is lower than 0.8. Moreover, the ferromagnetic correlation is strengthened markedly as the next-nearest-neighbor hopping energy increases. The resultant manipulation of ferromagnetism in graphene-based material may facilitate the development of spintronics.

Optical orientation in ferromagnet/semiconductor hybrids

The physics of optical pumping of semiconductor electrons in ferromagnet/semiconductor hybrids is discussed. Optically oriented semiconductor electrons detect the magnetic state of a ferromagnetic film. In turn, the ferromagnetism of the hybrid can be controlled optically with the help of a semiconductor. Spin–spin interactions near the ferromagnet/semiconductor interface play a crucial role in the optical readout and the manipulation of ferromagnetism.

Photomagnetic effects in III–V based magnetic semiconductors

Experimental results on the optical excitation of the III–V based magnetic semiconductor epilayers and related inhomogeneous systems are reviewed. Dynamic behaviors of optically induced magnetization rotation in the hole-mediated ferromagnetic semiconductor (Ga,Mn)As are discussed in terms of the newly proposed coupled hole-Mn spin complex for which hole and Mn spins rotate and relax together upon the optical excitation. Large photo-induced polar Kerr effect in the (Ga,Mn)As quantum wells, suggesting the enhanced magnetization rotation, is disclosed, from which manipulation of ferromagnetism through the dimensionality control of electronic states is discussed. Partial magnetization reversal by the electrical injection of hole spins has also been discussed on the basis of experimental results obtained from the (Ga,Mn)As-based magnetic tunnel junction devices. As to the room-temperature photo-enhanced magnetization (PEM) in the GaAs–Fe system, we found that the origin of PEM in the recently developed films is originated, at least partially, from the light-induced heating of the metamagnet Fe3Ga4. The contribution of photon-mode PEM is also discussed based on the experimental data.