Local spin valve effect in lateral (Ga,Mn)As/GaAs spin Esaki diode devices

We report on a local spin valve effect observed unambiguously in lateral all-semiconductor all-electrical spin injection devices, employing p+-(Ga,Mn)As/n+-GaAs Esaki diode structures as spin aligning contacts. We discuss the observed local spin-valve signal as a result of interplay between spin-transport-related contribution and tunneling anisotropic magnetoresistance of magnetic contacts. The magnitude of the spin-related magnetoresistance change is equal to 30 Ohm which is twice the magnitude of the measured non-local signal.Comment: submitted to Appl. Phys. Let

Tunneling Anisotropic Spin Polarization in lateral (Ga,Mn)As/GaAs spin Esaki diode devices

We report here on anisotropy of spin polarization obtained in lateral all-semiconductor all-electrical spin injection devices, employing $p^{+}-$(Ga,Mn)As/$n^{+}-$GaAs Esaki diode structures as spin aligning contacts, resulting from the dependence of the efficiency of spin tunneling on the orientation of spins with respect to different crystallographic directions. We observed an in-plane anisotropy of $~8$ in case of spins oriented either along $[1\bar{1}0]$ or $[110]$ directions and $~25$ anisotropy between in-plane and perpendicular-to-plane orientation of spins.Comment: 9 pages, 3 figure

Electrical spin injection and detection in lateral all-semiconductor devices

Electrical injection and detection of spin-polarized electrons is demonstrated for the first time in a single wafer, all-semiconductor, GaAs-based lateral spintronic device, employing p+-(Ga,Mn)As/n+-GaAs ferromagnetic Esaki diodes as spin aligning contacts. The conversion of spin-polarized holes into spin-polarized electrons via Esaki tunnelling leaves its mark in a bias dependence of the spin-injection efficiency, which at maximum reaches the relatively high value of 50%.Comment: 11 pages, 3 figures, sent to PR

Spin dynamics in semiconductors

This article reviews the current status of spin dynamics in semiconductors which has achieved a lot of progress in the past years due to the fast growing field of semiconductor spintronics. The primary focus is the theoretical and experimental developments of spin relaxation and dephasing in both spin precession in time domain and spin diffusion and transport in spacial domain. A fully microscopic many-body investigation on spin dynamics based on the kinetic spin Bloch equation approach is reviewed comprehensively.Comment: a review article with 193 pages and 1103 references. To be published in Physics Reports

Mapping the magnetic anisotropy in (Ga,Mn)As nanostructures

Anisotropic strain relaxation in (Ga,Mn)As nanostructures was studied combining time-resolved Kerr microscopy and ferromagnetic resonance techniques. Local resonance measurements on individual narrow stripes patterned along various crystallographic directions reveal that the easy axis of the magnetization can be forced perpendicular to the strain relaxation direction. Spatially resolved measurements on disk-shaped and rectangular (Ga,Mn)As structures allow us to directly visualize these local changes in the magnetic anisotropy. We show that the strain-induced edge anisotropy allows for an effective control of the coercive field in stripe structures

Spin-Injection into GaAs using ferromagnetic (Ga,Mn)As contacts

In our work we have employed a successful all electrical and all semiconductor spin injection scheme. Our samples base on a new class of so-called diluted magnetic semiconductors, namely its best known representative GaMnAs. In our experiments we were able to reliably achieve spin injection efficiencies of remarkably high 50% and slightly above. The results obtained from nonlocal in-plane spin-valve measurements were thereby consistent with our out-of-plane Hanle experiments in terms of injection efficiencies as well as spin diffusion lengths. These were roughly 3 µm, what corresponds to a spin lifetime in the range of 5 ns. We additionally investigated the anisotropies of tunneling MR and spin polarization. For in-plane TAMR we gained values of up to ≈ 1.5 % while for out-of-plane configuration we observed ≈ 8 %. In the case of in-plane TASP the effect had a magnitude of ≈ 8% and the out-of-plane TASP reached ≈ -25 %. For a second wafer with slightly lower doping of the conduction channel and thicker GaMnAs the spin diffusion length easily exceeded 10 µm. Our experiments on this second wafer have confirmed that a lithographically induced control of magnetic anisotropies in GaMnAs is possible due to strain relaxation of the GaMnAs layer perpendicular to the structure edges

Bias dependence of spin injection into GaAs from Fe, FeCo, and (Ga,Mn)As contacts

Spin injection from Fe(001) and (Ga,Mn)As(001) into n-GaAs(001) was investigated using a method which provides two-dimensional cross-sectional images of the spin polarization in GaAs. While the distribution of the spin polarization below the injecting contact is nearly uniform for (Ga,Mn)As, a strong confinement near the contact edge is observed for Fe and FeCo. The spin polarization in GaAs changes sign when the injected current is reversed. Multiple sign reversals as a function of bias voltage as reported previously for Fe injectors are not observed with (Ga,Mn)As and Fe contacts grown on clean n++−GaAs in agreement with earlier results for an epitaxial FeCo injector

In-plane anisotropy of tunneling magnetoresistance and spin polarization in lateral spin injection devices with (Ga,Mn)As/GaAs spin-Esaki diode contacts

We report here on in-plane anisotropy observed in the tunneling magnetoresistance of (Ga,Mn)As/n+-GaAs Esaki diode contacts and in the spin polarization generated in lateral all-semiconductor, all-electrical spin injection devices, employing such Esaki-diode structures as spin aligning contacts. The uniaxial component of the registered anisotropies, observed along [1 1 0] directions, does switch its sign as an effect of the applied bias, however the switching occurs at different bias values for magnetoresistance and for spin polarization cases

Affective responses in mountain hiking—A randomized crossover trial focusing on differences between indoor and outdoor activity

<div><p>Introduction</p><p>Affective responses during physical activity (PA) are important for engagement in PA programs and for adherence to a physically active lifestyle. Little is known about the affective responses to PA bouts lasting longer than 45 minutes. Therefore, the aims of the present study were to analyse acute effects on affective responses of a three-hour outdoor PA intervention (mountain hiking) compared to a sedentary control situation and to an indoor treadmill condition.</p><p>Methods</p><p>Using a randomized crossover design, 42 healthy participants were randomly exposed to three different conditions: outdoor mountain hiking, indoor treadmill walking, and sedentary control situation (approximately three hours each). Measures included the Feeling Scale, Felt Arousal Scale and a Mood Survey Scale. Repeated measures ANOVAs were used to analyse differences between the conditions.</p><p>Results</p><p>Compared to the control situation, the participants showed a significant increase in affective valence (<i>d</i> = 1.21, <i>p</i> < .001), activation (<i>d</i> = 0.81, <i>p</i> = .004), elation (<i>d</i> = 1.07, <i>p</i> < .001), and calmness (<i>d</i> = 0.84, <i>p</i> = .004), and a significant decrease in fatigue (<i>d</i> = -1.19, <i>p</i> < .001) and anxiety (<i>d</i> = -.79, <i>p</i> < .001) after mountain hiking. Outdoor mountain hiking showed significantly greater positive effects on affective valence, activation, and fatigue compared to indoor treadmill walking.</p><p>Discussion</p><p>The results indicate that a three-hour PA intervention (mountain hiking) elicits higher positive and lower negative affective responses compared to a sedentary control situation and to an indoor PA condition. Outdoor mountain hiking can be recommended by health professionals as a form of PA with the potential to positively influence affective responses.</p><p>Trial registration</p><p>ClinicalTrials.gov <a href="https://clinicaltrials.gov/ct2/show/NCT02853760" target="_blank">NCT02853760</a>. <a href="https://clinicaltrials.gov/" target="_blank">https://clinicaltrials.gov/</a>. Date of registration: 08/02/2016 (retrospectively registered). Date of enrolment of the first participant to the trial: 05/01/2014.</p></div

Affective responses (categorical) over time in each condition.

<p>Affective responses (categorical) over time in each condition.</p