Dilute ferromagnetic semiconductors: Physics and spintronic structures

Abstract

This review compiles results of experimental and theoretical studies on thin films and quantum structures of semiconductors with randomly distributed Mn ions, which exhibit spintronic functionalities associated with collective ferromagnetic spin ordering. Properties of p-type Mncontaining III-V as well as II-VI, IV-VI, V 2 -VI 3 , I-II-V, and elemental group IV semiconductors are described paying particular attention to the most thoroughly investigated system (Ga,Mn)As that supports the hole-mediated ferromagnetic order up to 190 K for the net concentration of Mn spins below 10%. Multilayer structures showing efficient spin injection and spin-related magnetotransport properties as well as enabling magnetization manipulation by strain, light, electric fields, and spin currents are presented together with their impact on metal spintronics. The challenging interplay between magnetic and electronic properties in topologically trivial and nontrivial systems is described, emphasizing the entangled roles of disorder and correlation at the carrier localization boundary. Finally, the case of dilute magnetic insulators is considered, such as (Ga,Mn)N, where low temperature spin ordering is driven by short-ranged superexchange that is ferromagnetic for certain charge states of magnetic impurities.

All-Wurtzite (In,Ga)As-(Ga,Mn)As Core–Shell Nanowires Grown by Molecular Beam Epitaxy

“…pattern for [11][12][13][14][15][16][17][18][19][20] zone axis fits well to the experimental image (see Fig. 3d).…”

Theory of Mn-doped II-II-V semiconductors

“…This dual role of Mn complicates theoretical understanding, including whether double exchange [11] is a relevant mechanism in these systems. The argument against double exchange is that it requires either different charge states [12] on Mn and/or the presence of an impurity band [4], which is a misconception that we will address later in this Letter. The coupled spin-and charge-doping also creates difficulties in establishing the connection between host properties and figures of merit [13].…”

“…Given the variation in the experimental data and the lack of any adjustable parameter, the agreement is excellent. It is worth noting that it is not well-accepted that DFT can be used to make useful predictions for DMS systems [4,12,39], so this success demonstrates that DFT analysis has a strong role to play in understanding this new class of systems. From these calculations we can predict that quenching, rather than slow cooling, may be advantageous for enhancing the magnetization per Mn, which can be as high as 3 µ B .…”

Systematic study of the spin stiffness dependence on phosphorus alloying in the ferromagnetic semiconductor (Ga,Mn)As

“…In this framework, diluted magnetic semiconductors (DMS) are a class of materials able to address this challenge. 1 More fundamentally, DMS and more specifically the III-V based (Ga,Mn)As have become in the past decade a benchmark material in order to achieve predictable tuning of magnetic properties. Levers such as the temperature, 2 the carrier concentration 3,4 but also the strain applied on the magnetic layer 5,6 or alloying with phosphorus 7,8 have been used in order to change the micromagnetic properties, e.g., the Curie temperature T C , the saturation magnetization M s , and the magnetic easy axis.…”