Spin-glass like behaviour of (Zn₁₋xMnx)₃As₂

Magnetic properties of the diluted magnetic semiconductor (Zn₁₋xMnx)₃As₂ (ZMA) have been investigated for compositions 0 ≤ x ≤ 0.13 and temperatures 4 K ≤ T ≤ 300 K. Several phenomena typical to spin-glasses were observed: history dependence, maxima in the functions Xdc(T) and Xac and smearing out of the maximum of Xdc(T) in strong fields. For samples with x = 0.10 and 0.13 our data give magnetic freezing temperatures around 200 K which is unusually high for diluted magnetic semiconductorsyesBelgorod State Universit

Heat Treatment Effect on Magnetic Microstructure of Fe73.9Cu1Nb3Si13.2B8.9 Thin Films

Fe73.9Cu1Nb3Si13.2B8.9 (Finemet) thin films were deposited on the glass substrates by means of radio frequency sputtering. The films thickness was varied from 10 to 200 nm. Heat treatment at temperatures of 350, 400 and 450 °C were performed for 30 minutes in order to control thin film structural state. The X-ray powder diffractometry revealed that the crystallization of α-FeSi nanograins took place only at 450 °C whilst the other samples stayed in the amorphous state. Relation between the structure and magnetic properties of the films was discussed in the framework of random magnetic anisotropy model and the concept of stochastic magnetic domains. The latter was investigated using magnetic force microscopy (MFM). MFM data showed formation of such magnetic domains only in samples thermally treated at 450 °C. There was a tendency of the magnetic domain size reduction with the thickness decrease. © 2018 The Authors, published by EDP Sciences.The research was supported by the Ministry of Education and Science of the Russian Federation Agreement no. 02.A03.21.0006 and project no. 3.6121.2017

Релаксация спина марганца в ферромагнитном (Ga,Mn)As

В работе предложена теория спиновой релаксации 3d⁵-электронов марганца в (Ga,Mn)As, включая ферромагнитную и парамагнитную фазы. В арсениде галлия, легированном марганцем, дырки проявляют себя двояко: как переносчики магнитного взаимодействия между центрами марганцев и как канал для их спиновой релаксации. Сильное спин-орбитальное взаимодействие дырок приводит к коротким временам их спиновой релаксации, а обменное взаимодействие дырок с 3d⁵-электронами марганца вызывает его быструю спиновую релаксацию. Данный механизм спиновой релаксации марганца доминирует в ферромагнитной фазе, а в парамагнитной фазе основной механизм спиновой релаксации Mn обусловлен флуктуациями спина дырок.Запропоновано теорію спінової релаксації 3d⁵-електронів марганцю в (Ga,Mn)As, включаючи феромагнітну та парамагнітну фази. У арсеніді галію, який леговано марганцем, дірки проявляють себе двояко: як переносники магнітної взаємодії між центрами марганців і як канал для їх спінової релаксації. Сильна спін-орбітальна взаємодія дірок призводить до коротких часів їх спінової релаксації, а обмінна взаємодія дірок з 3d⁵-електронами марганцю викликає його швидку спінову релаксацію. Цей механізм спінової релаксації марганцю домінує у феромагнітній фазі, а в парамагнітній фазі основний механізм спінової релаксації Mn обумовлено флуктуаціями спіна дірок.A theory of spin relaxation of 3d⁵-electrons of manganese in (Ga,Mn)As, including ferromagnetic and paramagnetic phases, is presented. In manganese doped gallium arsenide, holes act in two ways: as carriers of magnetic interactions between manganese centers and as a channel for their spin relaxation. The strong spin-orbital interactions of the holes lead to short spin relaxation times and exchange interactions of the holes with the 3d⁵-electrons of manganese cause its rapid spin relaxation. This mechanism for spin relaxation of manganese predominates in the ferromagnetic phase, while the main mechanism for spin relaxation of Mn in the paramagnetic phase is through fluctuations in the hole spins

Configuration interaction in delta-doped heterostructures

We analyze the tunnel coupling between an impurity state located in a δ-layer and the 2D delocalized states in the quantum well (QW) located at a few nanometers from the δ-layer. The problem is formulated in terms of Anderson–Fano model as configuration interaction between the carrier bound state at the impurity and the continuum of delocalized states in the QW. An effect of this interaction on the interband optical transitions in the QW is analyzed. The results are discussed regarding the series of experiments on the GaAs structures with a δ-Mn layer

Pecularities of Hall effect in GaAs/{\delta}<Mn>/GaAs/In\timesGa1-\timesAs/GaAs (\times {\approx} 0.2) heterostructures with high Mn content

Transport properties of GaAs/{\delta}/GaAs/In\timesGa1-\timesAs/GaAs structures containing InxGa1-xAs (\times {\approx} 0.2) quantum well (QW) and Mn delta layer (DL) with relatively high, about one Mn monolayer (ML) content, are studied. In these structures DL is separated from QW by GaAs spacer with the thickness ds = 2-5 nm. All structures possess a dielectric character of conductivity and demonstrate a maximum in the resistance temperature dependence Rxx(T) at the temperature {\approx} 46K which is usually associated with the Curie temperature Tc of ferromagnetic (FM) transition in DL. However, it is found that the Hall effect concentration of holes pH in QW does not decrease below TC as one ordinary expects in similar systems. On the contrary, the dependence pH(T) experiences a minimum at T = 80-100 K depending on the spacer thickness, then increases at low temperatures more strongly than ds is smaller and reaches a giant value pH = (1-2)\cdot10^13 cm^(-2). Obtained results are interpreted in the terms of magnetic proximity effect of DL on QW, leading to induce spin polarization of the holes in QW. Strong structural and magnetic disorder in DL and QW, leading to the phase segregation in them is taken into consideration. The high pH value is explained as a result of compensation of the positive sign normal Hall effect component by the negative sign anomalous Hall effect component.Comment: 19 pages, 6 figure

Anomalous cyclotron mass dependence on the magnetic field and Berry’s phase in (Cd₁-x-γZnxMnγ)₃As₂ solid solutions

Shubnikov-de Haas (SdH) effect and magnetoresistance measurements of single crystals of diluted II-V magnetic semiconductors (Cd₁-x-γZnxMnγ)₃As₂ (x+γ= 0.4, y=0.04 and 0.08) are investigated in the temperature range T=4.2 ÷ 300 K and in transverse magnetic field B=0 ÷ 25