High Curie temperature and perpendicular magnetic anisotropy in homoepitaxial InMnAs films

Abstract

Abstract:We have prepared the dilute magnetic semiconductor (DMS) InMnAs with different Mn concentrations by ion implantation and pulsed laser melting. The Curie temperature of the In 1-x Mn x As epilayer depends on the Mn concentration x, reaching 82 K for x=0.105. The substitution of Mn ions at the Indium sites induces a compressive strain perpendicular to the InMnAs layer and a tensile strain along the in-plane direction. This gives rise to a large perpendicular magnetic anisotropy, which is often needed for the demonstration of electrical control of magnetization and for spin-transfer-torque induced magnetization reversal.

The Al Doping Effect on Epitaxial (In,Mn)As Dilute Magnetic Semiconductors Prepared by Ion Implantation and Pulsed Laser Melting

“…As a result, the maximal Mn concentration is 14.7% when the implanting fluence is 2.4 × 10 16 /cm 2 , and the average doping concentration is around 12%. However, according to our previous study [ 24 ], the only-Mn-doped sample exhibited an average Mn concentration of 8.7% in the doped region, due to the diffusion of Mn caused by pulsed laser-induced liquid phase epitaxy. For Al implantation, the average concentrations are calculated as 6% and 12%, respectively, when the implantation fluences are selected as 1.7 × 10 16 /cm 2 and 3.4 × 10 16 /cm 2 .…”

“…The InMnAlAs-0 sample presents a typical ferromagnetic feature, i.e., highly square-like hysteresis loop with a low coercivity field (107 Oe) and a magnetization of ~23 emu/cm 3 . According to Figure 4 b, the sample shows a high T C of 80 K where the magnetization vanishes [ 24 ]. Moreover, the M-T curve shows a concave-like shape, and this is reminiscent of mean-field theory approximation [ 5 , 24 , 29 ].…”

“…According to Figure 4 b, the sample shows a high T C of 80 K where the magnetization vanishes [ 24 ]. Moreover, the M-T curve shows a concave-like shape, and this is reminiscent of mean-field theory approximation [ 5 , 24 , 29 ]. The magnetic field and temperature dependent magnetization both unambiguously prove the ferromagnetic nature of our virgin (In,Mn)As.…”

“…Actually, the suppression of magnetization and Curie temperature induced by Al doping has been observed in a series of (Ga,Mn)As samples [ 13 ]; in a study by [ 3 ], there were two different mechanisms proposed: (i) part of Mn atoms are driven into the interstitial sites; and (ii) the localization of carriers is enhanced by Al alloying due to stronger p-d exchange coupling However, in the low Al concentration doped region (<20%), the first function worked dominantly, and a similar phenomenon appeared in Zn-doped (Ga,Mn)As according to our previous research [ 14 ]. This is the most probable explanation for the Al-doped (In,Mn)As case, since, for the highest Al concentration doped sample, it is observed that in addition to the reduction in Curie temperature, the M–T curve deviates from the mean-field approximation, and such a phenomenon is in good agreement with a decrease in substitutional Mn concentration [ 24 ]. Unfortunately, it is extremely difficult to examine the effect of enhanced localization [ 24 , 25 ] in our sample, because of the conducting InAs substrate.…”

“…For the annealing process, a UV pulsed laser with nanosecond pulse was employed for the recrystallization. The pulsed laser treatment with a 28 ns duration was performed in air atmosphere, and an energy of 0.2 J/cm 2 was selected, which is the optimal annealing condition for InAs recrystallization [ 21 , 24 ]. The wavelength of the pulse laser is 308 nm.…”