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The formation of a magnetic dead layer at the interfaces of the perovskite oxide La0.67Sr0.33 MnO3 (LSMO) is one of the crucial issues for its spintronic applications. In this letter, we report the reduction of the dead layer by growing LSMO on a LaMnO3 (LMO) layer. Furthermore, we detect tunneling magnetoresistance (TMR) in an LSMO/LMO/LSMO heterostructure. The obtained sign of the TMR was negative, but it changed to positive after annealing. This unusual negative TMR can be attributed to the intrinsic structural difference between the upper and lower interfaces of LMO and can be understood by a weak antiferromagnetic metallic thin layer formed at the upper LSMO/LMO interface. This layer is thought to be formed by diffused Sr atoms and oxygen vacancies in the LMO barrier. Our results indicate that control of intermixing of atoms at the interfaces is a key to controlling the TMR. [ABSTRACT FROM AUTHOR]

We show high-temperature ferromagnetism in heavily Fe-doped ferromagnetic semiconductor (Ga1-x,Fex)Sb (x = 23% and 25%) thin films grown by low-temperature molecular beam epitaxy. Magnetic circular dichroism spectroscopy and anomalous Hall effect measurements indicate intrinsic ferromagnetism of these samples. The Curie temperature reaches 300K and 340K for x = 23% and 25%, respectively, which are the highest values reported so far in intrinsic III-V ferromagnetic semiconductors. [ABSTRACT FROM AUTHOR]

We investigate the crystal structure, transport, and magnetic properties of Fe-doped ferromagneticsemiconductor (Al1−x,Fex)Sb thin films up to x = 14% grown by molecular beam epitaxy. All the samples show p-type conduction at room temperature and insulating behavior at low temperature. The (Al1−x,Fex)Sb thin films with x ≤ 10% maintain the zinc blende crystal structure of the host materialAlSb. The (Al1−x,Fex)Sb thin film with x = 10% shows intrinsic ferromagnetism with a Curie temperature (TC) of 40 K. In the (Al1−x,Fex)Sb thin film with x = 14%, a sudden drop of the hole mobility and TC was observed, which may be due to the microscopic phase separation. The observation of ferromagnetism in (Al,Fe)Sb paves the way to realize a spin-filtering tunnel barrier that is compatible with well-established III-V semiconductor devices. [ABSTRACT FROM AUTHOR]

A p-type ferromagnetic semiconductor (Ga1_x,Fex)Sb (x = 3.9%-13.7%) has been grown by lowtemperature molecular beam epitaxy (MBE) on GaAs(001) substrates. Reflection high energy electron diffraction patterns during the MBE growth and X-ray diffraction spectra indicate that (Ga,Fe)Sb layers have the zinc-blende crystal structure without any other crystallographic phase of precipitates. Magnetic circular dichroism (MCD) spectroscopy characterizations indicate that (Ga,Fe)Sb has the zinc-blende band structure with spin-splitting induced by s,p-d exchange interactions. The magnetic field dependence of the MCD intensity and anomalous Hall resistance of (Ga,Fe)Sb show clear hysteresis, demonstrating the presence of ferromagnetic order. The Curie temperature (TC) increases with increasing x and reaches 140 K at x = 13.7%. The crystal structure analyses, magneto-transport, and magneto-optical properties indicate that (Ga,Fe)Sb is an intrinsic ferromagnetic semiconductor. [ABSTRACT FROM AUTHOR]

We systematically investigated the influence of strain on the electronic structure and ferromagnetism of (In,Fe)As thin films. It is found that while the shift of the critical point energies of compressive-strained (In,Fe)As layers grown on (In1-y,Gay)As (y=0.05, 0.1) buffer layers can be explained by the hydrostatic deformation effect (HDE) alone, those of tensile-strained (In,Fe)As layers grown on (Ga1-z,Alz)Sb (z=0, 0.5, 1) buffer layers can be explained by the combination of HDE and the quantum confinement effect (QCE). The Curie temperature TC of the (In,Fe)As layers strongly depends on the strain, and shows a maximum for the (In,Fe)As layer grown on a GaSb buffer layer. The strain dependence of TC can be explained by the s-d exchange mechanism taking into account HDE and QCE. [ABSTRACT FROM AUTHOR]

We demonstrated the control of ferromagnetism in a surface quantum well containing a 5 nm-thick n-type ferromagnetic semiconductor (FMS) (In,Fe)As layer sandwiched between two InAs layers, by manipulating the carrier wavefunction. The Curie temperature (TC) of the (In,Fe)As layer was effectively changed by up to 12K (ΔTC/TC=55%). Our calculation using the mean-field Zener theory reveals an unexpectedly large s-d exchange interaction in (In,Fe)As. Our results establish an effective way to control the ferromagnetism in quantum heterostructures of n-type FMSs, as well as require reconsideration on the current understanding of the s-d exchange interaction in narrow gap FMSs [ABSTRACT FROM AUTHOR]