arXiv subjects

A. Oiwa

Publications and source records attributed to A. Oiwa.

23 records · Page 2Linked to original sources

arXiv2003

Cyclotron Resonance in Ferromagnetic InMnAs/(Al,Ga)Sb Heterostructures

We report the observation of hole cyclotron resonance (CR) in InMnAs/(Al,Ga)Sb heterostructures in a wide temperature range covering both the paramagnetic and ferromagnetic phases. We observed two pronounced resonances that exhibit drastic changes in position, linewidth, and intensity at a temperature higher than the Curie temperature, indicating possible local magnetic ordering or clustering. We attribute the two resonances to the fundamental CR transitions expected for delocalized valence-band holes in the quantum limt. Using an 8-band {\bf k$\cdot$p} model, which incorporates ferromagnetism within a mean-field approximation, we show that the temperature-dependent CR peak shift is a direct measure of the carrier-Mn exchange interaction. Significant line narrowing was observed at low temperatures, which we interpret as the suppression of localized spin fluctuations.

cond-mat.mes-hall↗

arXiv2002

Ultrafast optical manipulation of ferromagnetic order in InMnAs/GaSb

We have performed a two-color time-resolved magneto-optical Kerr effect (MOKE) study of a ferromagnetic InMnAs/GaSb heterostructure. We observed ultrafast photo-induced changes in the MOKE signal induced by a large density of spin-polarized transient carriers created only within the InMnAs layer using intense 140 fs mid-infrared pulses. Our data clearly demonstrates that magnetic properties, e.g., remanence and coercivity, can be strongly modified. The dependence of these changes on the time delay, pump polarization, pump intensity, and sample temperature is discussed.

cond-mat.mtrl-sci↗

arXiv2002

Cyclotron Resonance of Itinerant Holes in Ferromagnetic InMnAs/GaSb Heterostructures

We report the first observation of hole cyclotron resonance (CR) in ferromagnetic InMnAs/GaSb heterostructures both in the high-temperature paramagnetic phase and the low-temperature ferromagnetic phase. We clearly resolve two resonances that exhibit strong temperature dependence in position, linewidth, and intensity. We attribute the two resonances to the so-called fundamental CR transitions expected for delocalized holes in the valence band in the magnetic quantum limit, demonstrating the existence of $p$-like itinerant holes that are describable within the Luttinger-Kohn effective mass theory.

cond-mat.mtrl-sci↗

arXiv2002

Electronic structure of In$_{1-x}$Mn$_x$As studied by photoemission spectroscopy: Comparison with Ga$_{1-x}$Mn$_x$As

We have investigated the electronic structure of the $p$-type diluted magnetic semiconductor In$_{1-x}$Mn$_x$As by photoemission spectroscopy. The Mn 3$d$ partial density of states is found to be basically similar to that of Ga$_{1-x}$Mn$_x$As. However, the impurity-band like states near the top of the valence band have not been observed by angle-resolved photoemission spectroscopy unlike Ga$_{1-x}$Mn$_x$As. This difference would explain the difference in transport, magnetic and optical properties of In$_{1-x}$Mn$_x$As and Ga$_{1-x}$Mn$_x$As. The different electronic structures are attributed to the weaker Mn 3$d$ - As 4$p$ hybridization in In$_{1-x}$Mn$_x$As than in Ga$_{1-x}$Mn$_x$As.

cond-mat.mtrl-sci↗

arXiv2002

Ferromagnetic semiconductor (In,Ga,Mn)As with Curie temperature above 100 K

We have grown (InyGa1-y)1-xMnxAs ferromagnetic semiconductor layers with Mn composition x up to 0.13 on InP substrates by molecular beam epitaxy. Near the lattice-matched composition, i.e., y ~ 0.53, the Curie temperature increases linearly with the ferromagnetically effective Mn composition x_eff, following the empirical equation T_C=1300x_eff. We obtained Curie temperatures above 100 K when x is relatively high (x>0.1; x_eff>0.08) and the hole concentration is in the order of 10^19 cm^-3.

cond-mat.mtrl-sci↗