Curie Point Singularity in the Temperature Derivative of Resistivity in (Ga,Mn)As

Abstract

We observe a singularity in the temperature derivative drho/dT of resistivity at the Curie point of high-quality (Ga,Mn)As ferromagnetic semiconductors with Tc's ranging from approximately 80 to 185 K. The character of the anomaly is sharply distinct from the critical contribution to transport in conventional dense-moment magnetic semiconductors and is reminiscent of the drho/dT singularity in transition metal ferromagnets. Within the critical region accessible in our experiments, the temperature dependence on the ferromagnetic side can be explained by dominant scattering from uncorrelated spin fluctuations. The singular behavior of drho/dT on the paramagnetic side points to the important role of short-range correlated spin fluctuations.

The essential role of carefully optimized synthesis for elucidating intrinsic material properties of (Ga,Mn)As

“…The sample has sharp Curie point singularities in magnetization and electrical transport typical of uniform, high-quality itinerant ferromagnets (Fig. 1a) 11 . Magnetization precession damping factor and spinwave resonances (SWRs) obtained from MO measurements (Fig.…”

“…Because of the highly non-equilibrium nature of the heavily-doped ferromagnetic (Ga,Mn)As, the growth and post-growth annealing procedures have to be individually optimized for each Mn-doping level to obtain films that are as close as possible to idealized uniform (Ga,Mn)As mixed crystals with the minimal density of compensating and other unintentional defects. An extensive set of characterization measurements has to accompany the synthesis to guarantee that the materials show systematic doping trends; monitoring the thermodynamic Curie point singularities is essential for assuring the uniformity and high magnetic quality of the materials 11,15,54,55 . When omitting the above procedures, extrinsic impurities and sample inhomogeneities can yield nonsystematic doping trends and conceal the intrinsic magnetic properties of (Ga,Mn)As.…”

“…A key characterization tool is the thermodynamic Curie point singularity 11 . The development of sharply vanishing magnetization M(T) at T C and the onset of the singularity in dr/dT are well correlated with increasing T C and conductivity within the annealing sequence.…”

Энергетическая структура одиночного акцептора Mn в GaAs : Mn

“…Экситоны в кристаллах и полупроводниковых наноструктурах"Сообщалось о создании образцов с температурами Кюри T C до 185 К [15], то есть, значительно выше температуры жидкого азота N 2 , и нет доказательств фун-даментального предела для получения более высоких значений [16].…”

Magnetic coupling in ferromagnetic semiconductor (Ga,Mn)As/(Al,Ga,Mn)As bilayers

“…(Ga,Mn)As is a well-studied DMS which exhibits ferromagnetic behavior due to a coupling of the local magnetic moments via delocalized charge carriers, both provided by the substitutional Mn. 2,3 The highest Curie temperature (T C ) of this material is around 190 K. [4][5][6] The magnetic properties of (Ga,Mn)Asbased multilayers are highly tunable through manipulation of parameters such as the Mn concentration, epitaxial strain, and doping. For example, while the interlayer exchange coupling is usually ferromagnetic in (Ga,Mn)As/GaAs/(Ga,Mn)As structures, 7,8 antiferromagnetic alignment can be realized by p-type doping of the GaAs spacer.…”