Development of Co-Rich Microwires with Graded Magnetic Anisotropy

In this paper, a gradual change in the hysteresis loop of Co-rich glass-coated microwire stress-annealed at variable temperature is observed. Such microwires annealed with a temperature gradient also present a variable squareness ratio and magnetic anisotropy field along the microwire’s length. The obtained graded anisotropy has been attributed to a gradual modification of the domain structure along the microwire originated by a counterbalance between shape, magnetoelastic, and induced magnetic anisotropies. Accordingly, we propose a rather simple route to design graded magnetic anisotropy in a magnetic microwire.

THERMAL-INDUCED DOMAIN PROCESSES IN TRIGLYCINE SULFATE CRYSTALS WITH CHROMIUM IMPURITIES

В работе представлены результаты исследований термоиндуцированных доменных процессов в хромсодержащих кристаллах триглицинсульфата. Показано, что изменение температуры кристаллов ТГС: Cr в отсутствие внешних электрических полей сопровождается перестройкой доменной структуры, которая наиболее интенсивно происходит в области фазового перехода. Деполяризующее поле величиной ~1,4·10 В·м, которое порождается градиентным изменением температуры образца, вызывает процесс переключения его доменной структуры. В неотожженных кристаллах при концентрациях примеси, превышающих 5·10 вес. % процессы переключения затруднены, а интенсивность термоиндуцированных доменных процессов существенно ниже аналогичных для образцов с меньшим содержанием примеси. На интенсивность процессов переключения кристаллов ТГС: Cr существенное влияние оказывает скорость их нагревания. Зависимости интегрального числа скачков переполяризации от скорости нагревания образцов N = f (V) носят экстремальный характер. Экстремумы кривых N = f (V) лежат в интервалах скоростей (0,2-0,8) K·c. Доменная структура кристаллов ТГС:Cr состоит из матрицы основного домена, линзовидных и ламелеобразных доменов. Под воздействием электронного пучка наблюдается эволюция доменной структуры, сопровождающаяся ростом доменов, их слиянием и переключением образца. Высокотемпературный отжиг кристаллов приводит к их полидоменизации. The article presents the results of studies of thermally induced domain processes in chromium-containing crystals of triglycine sulfate (TGS). It is shown that a change in the temperature of TGS: Cr crystals in the absence of external electric fields is accompanied by a rearrangement of the domain structure, that occurs most intensively in the region of the phase transition. A depolarizing field of ~1,4·10 V·m, which is generated by a gradient change in the temperature of the sample, causes the process of switching its domain structure. In unannealed crystals at impurity concentrations exceeding 5·10 wt.%, switching processes are hindered, and the intensity of thermally induced domain processes is significantly lower than that for samples with a lower impurity content. The intensity of the switching processes of TGS: Cr crystals is significantly influenced by the rate of their heating. The dependences of the integral number of polarization-reversal jumps on the heating rate of the samples N = f (V) are extreme. The extrema of the N = f (V) curves lie in the rate intervals (0,2 - 0,8) K·c. The domain structure of TGS: Cr crystals consists of a matrix of the main domain, lenticular and lamellar domains. Evolution of the domain structure is observed under the influence of an electron beam, accompanied by the growth of domains, their coalescence, and sample switching. High-temperature annealing of crystals leads to their polydomenization.

Reactive RF magnetron sputtering epitaxy of NiO thin films on (0001) sapphire and (100) MgO substrates

Epitaxial growths of NiO thin films were realized on (0001) sapphire and (100) MgO substrates by using a reactive RF magnetron sputtering method. The NiO epilayers grown on a (0001) sapphire exhibited the (111)-oriented double-domain structure, which comprised of a triangular and its inverted triangular grains. Meanwhile, the NiO epilayers on a (100) MgO exhibited the (100)-oriented single-domain structure, which comprised of quadrangular grains. The observed grain structures most likely reflect the growth planes of respective NiO epilayers, and, mixed crystals of NiO and MgO were present near the interface. Therefore, A (100) MgO substrate is suitable for obtaining a single-domain NiO epilayer, whereas a (0001) sapphire substrate is suitable for obtaining a NiO epilayer without interdiffusion between NiO and sapphire. These NiO epilayers will be expected for applying the physical properties evaluation using photoluminescence or Hall measurements, and the fabrication of electrical or optical devices.