We used the Taylor-Ulitovsky Technique to prepare nanocrystalline Co2MnGe Heusler alloy glass-coated microwires with a metallic nucleus diameter of 18 ± 0.1 µm and a total diameter of 27.2 ± 0.1 µm. Magnetic and structural studies were carried out to determine the fundamental magneto-structural characteristics of Co2MnGe glass-coated microwires. XRD revealed a well-defined nanocrystalline structure with average grain size about 63 nm, lattice parameter a = 5.62 and a unique mixture of L21 and B2 phases. The magnetization curves for field cooling and field heating (FC-FH) demonstrate a considerable dependence on the applied magnetic field, ranging from 50 Oe to 20 kOe. Internal stresses, originated by the production process, resulted in various magnetic phases, which were responsible for the notable difference of field cooling (FC) and field heating (FH) curves on magnetization dependence versus temperature. Furthermore, the ferromagnetic behavior and expected high Curie temperature together with high degree of L21 ordered makes it a promising candidate for many applications.

The direct measurements of the magnetocaloric effect were performed in Heusler Ni44.4Mn36.2Sn14.9Cu4.5 alloy at cryogenic temperatures in magnetic fields up to 10 T. The maximum value of the inverse magnetocaloric effect in a field of 10 T was observed ∆Tad = –2.7 K in the vicinity of the 1st order magnetostructural phase transition at T0 = 117 K. The ab initio and Monte Carlo calculations were performed to discuss the effect Cu doping into Ni-Mn-Sn compound on the ground state structural and magnetic properties. It is shown that with increasing Cu content the martensitic transition temperature decreases and the Curie temperature of austenite slightly increases. In general, calculated transition temperatures, magnetization values are correlated well with the experimental ones.

We studied Ni2FeSi, Co2FeSi and Co2MnSi -based full Heusler alloy glass-coated microwires with the same geometric aspect ratio ρ ≈ 0.50 ± 0.01 prepared using Taylor-Ulitovsky method. The fabrication of X2YZ; (X = Co & Ni, Y = Fe & Mn and Z = Si) based glass coated microwires with fixed aspect ratio is a quite challenging due to the different samples preparation conditions. The XRD analysis shows nanocrystalline microstructure for all the samples. Space group Fm3¯m (FCC) with disordered B2 and A2-types for Ni2FeSi and Co2FeSi and ordered L21-type for Co2MnSi are observed. The change in the positions of Ni, Co and Mn, Fe in X2YSi resulted in a variation in the lattice cell parameters and the average grain size of the sample. Room temperature magnetic behavior shows a dramatic change depending on the chemical composition, where Ni2FeSi-MWs shows the highest coercivity (Hc) compared to Co2FeSi-MWS and Co2MnSi-MWs. The Hc –value of Ni2FeSi-MWs is 16 times higher than that of Co2MnSi-MWs and 3 times higher than that of Co2FeSi-MWS. Meanwhile, the highest reduced remanence is reported for Co2FeSi-MWS (Mr =0.92), , being about 0.33 and 0.22 for Ni2FeSi-MWs and Co2MnSi-MWs, respectively. From the analysis of the temperature dependence of the magnetic properties (Hc and Mr) of X2YZ-MWs we deduced that Hc shows a stable tendency for Co2MnSi-MWs and Co2FeSi-MWs, meanwhile two flipped points are observed for Ni2FeSi-MWs where the behavior of Hc changes with temperature. For Mr monotonic increase by decreasing the temperature is observed for Co2FeSi-MWs and Ni2FeSi-MWs and roughly stable for Co2MnSi-MWs. The thermomagnetic curves at low magnetic field show irreversible magnetic behavior for Co2MnSi-MWs and Co2FeSi-MWs and regular ferromagnetic behavior for Ni2FeSi-MWs. The current result illustrates the ability to tailor the structure and magnetic behavior of X2YZ-MWs at a fixed internal stresses, i.e., with fixed aspect ratio. Additionally, a different behavior was revealed in X2YZ-MWs depending on the degree of ordering and elements distribution. The tunability of magnetic properties of X2YZ-MWs makes them suitable for sensing applications.

We studied the effect of annealing and the applied magnetic field from 50 Oe to 20 kOe on the magneto-structural behavior of Ni2FeSi-based Heusler microwires fabricated by using Taylor-Ulitovsky technique. Using the XRD analysis, a strong effect of annealing, manifested as the development of the crystallization process, was observed. The average grain size and crystalline phase content of annealed sample increase from 21.3 nm and 34 % to 32.8 nm and 79%, respectively, as-compared to the as-prepared one. In addition, upon annealing phase transforms into a monoclinic martensitic structure with modulation 10M were observed, which cannot be found in the as-prepared sample. Concerning the magnetic properties, both samples show ferromagnetic behavior below and above the room temperature, where the Curie temperature of Ni2FeSi is higher than room temperature. The induced secondary phases have a noticeable effect on the magnetic behavior of the annealed sample, where a high normalized saturation magnetization (NMs) and low normalized reduced remenance (Mr = M/M5K), compared to the as- prepared have been detected. Additionally, the coercivity of annealed sample shows one flipping point at 155 K where it behavior with temperature is changed. Meanwhile, the as-prepared sample show two flipped point at 205 K and 55 K. A mismatch between field cooling (FC) and field heating (FH) magnetization curves with temperature has been detected for annealed sample at low applied magnetic field. In addition the FC and FH curves shows different slopes with variation the temperature and the magnetic field. By increasing the external magnetic field higher than 200 Oe and up to 20 kOe a gradual changing in the magnetic behavior has been detected, where the mismatch and different slopes disappeared at applying magnetic field about 20 kOe. The difference in magnetic and structure behavior of Ni2FeSi microwires sample is discussed considering the effect of induced internal stresses by the presence of a glass coating and the recrystallization and stresses relaxation upon annealing.

The present study illustrates the strong effect of geometrical parameters on the magneto-structural properties of Co2MnSi glass-coated microwires prepared using the Taylor-Ulitovsky method. Thus, two samples with different geometrical aspect ratios (ρ= d / D) have been fabricated, where d is the metallic nuclei diameter and D is the total diameter of the Co2MnSi microwire. The XRD analysis shows a significant change by modifying the aspect ratio, for ρ = 0.46 the main peak with miller indices (220) is recognized as an A2-type disordered cubic structure. Meanwhile, in the sample with a low aspect ratio, ρ = 0.31, the perfect L21 ordered cubic structure is attained. In addition, a decrease in average grain size from 36.62 nm to 28.07 nm by increasing the aspect ratio from 0.46 to 0.31 is observed. The magnetic characterization has been done in a wide range of temperatures and magnetic fields. Both of Co2MnSi samples show ferromagnetic behavior in a whole measuring temperatures range. A significant increase in coercivity and normalized reduced remanence by decreasing the aspect ratio is observed. The change in the magnetic properties is attributed to the modification in the microstructure, which is induced during the fabrication process. Such a dependence on the microstructure and magnetic properties on the ρ-ratio can be associated either with the internal stresses distribution and magnitude or with different quenching rates of microwires with different aspect ratios. The current findings demonstrate the tunability of microstructure and magnetic properties of Co2MnSi-glass-coated microwires simply, by a small modification in the geometric properties during the manufacturing process and without excreting any additional post-processing. The variation in geometric parameters of Co2MnSi glass-coated microwires allows us to tune magnetic properties and structure, which is essentially advantageous for sensing devices development.

In current work, we illustrate the effect of adding small amount of Carbon to very common Co2MnSi Heusler alloy based-glass coated microwires. A significant change in the magnetic and structure structural properties has observed for the new alloy Co2MnSiC compared to the Co2MnSi alloy. The magneto-structural investigations have performed to clarify the main phys-ical parameters i.e., structural & magnetic at a wide range of measuring temperature. The XRD analysis illustrated the well-defined crystalline structure with average grain size (Dg = 29.16 nm) and a uniform cubic structure with A2-type compared to the mixed L21 and B2 cubic structures for Co2MnSi-based glass coated microwires. The magnetic behaviour has investigated at a tem-perature range (5 to 300 K) and an external applied magnetic field (50 Oe to 20 kOe). The adding of small amount of Carbon to the Co2MnSi matrix enhance the magnetic thermal stability, where the thermomagnetic behaviour of Co2MnSiC glass-coated microwires show a perfect stable be-haviour for a temperature range from 300 K to 5 k, the differences between the coercivity value is only 0.3 Oe compared to 4 Oe for Co2MnSi-sample. In addition, M-H loops measured at tempera-ture below 50 K show unsaturated loops; meanwhile the Co2MnSi loops shows a strong antifer-romagnetic coupling for the loops measured below 50 K. By studying the field cooling (FC) and field heating (FH) magnetizations curves at a wide range of external applied magnetic field we detected a critical magnetic field (H = 1 kOe) where FC and FH curves have a stable magnetic behavior for Co2MnSiC sample, such stability does not find in Co2MnSi sample. We proposed a phenomenal expression to estimate the magnetization thermal stability, ΔM (%), of FC and FH magnetization curves and the maximum value is detected at the critical magnetic field where ΔM (%) ≈ 98 %. The promising magnetic stability of Co2MnSiC glass-coated microwires with tem-perature is due to the changing of the microstructure induced by adding Carbon, as the A2-type structure show a unique stability by variation the temperature and the external magnetic field. In addition, a unique internal mechanical stress, which induced during the fabrication process and plays on controlling magnetic behavior with temperature and external magnetic field. The ob-tained results make Co2MnSiC promising candidate for magnetic sensing devices based Heusler glass-coated microwires.

In current study we have obtained Co2FeSi-glass coated microwires with different geometrical aspect ratio, ρ = d/Dtot (diameter of metallic nucleus, d and total diameter, Dtot). The structure and magnetic properties are investigated at a wide range of temperature. XRD analysis illustrates a notable changing in the microstructure by increasing the aspect ratio of Co2FeSi glass coated microwires. Amorphous structure is detected for the sample with the lowest aspect ratio (ρ = 0.23), whereas a growth of crystalline structure is observed in the other samples (aspect ratio ρ = 0.30 and 0.43). This change at the microstructure properties correlates with dramatic changing in magnetic properties. For the sample with the lowest ρ -ratio, non-perfect square loops are obtained with low normalized remanent magnetization. A notable enhancement in the squareness and coercivity are obtained by increasing ρ -ratio. Changing the internal stresses strongly affects the microstructure, resulting in a complex magnetic reversal process. The thermomagnetic curves show large irreversibility for the Co2FeSi with low ρ -ratio. Meanwhile, if we increase the ρ -ratio, the sample shows perfect ferromagnetic behavior without irreversibility. The current result illustrates the ability to control the microstructure and magnetic properties of Co2FeSi-glass-coated microwires by changing only their geometric properties without performing any addition heat treatment. The modification of geometric parameters of Co2FeSi glass-coated microwires allows to obtain microwires which exhibit an unusual magnetization behavior that offers opportunities to understand the phenomena of various types of magnetic domain structures, which is essentially helpful for designing sensing devices based on thermal magnetization switching.

Heusler Ni-Mn-Ga alloys with martensitic transformation being multiferroic materials are touted for magneto- and multi-caloric effect (MCE) and moreover, they exhibit magnetic shape memory (MSM) phenomena. MCE benefits from high saturation magnetization and also large variability and sensitivity of transformation temperatures on alloying. In contrast, MSM phenomena are limited by low temperatures of both ferromagnetic and ferroelastic transformations. In an attempt to increase the transformation temperatures and to understand the physical fundamentals beyond transformation variations and magnetic ordering, we experimentally investigate the magnetic and transformation properties in Ni2MnGa alloyed with transitional elements spanning from Cr to Cu. These elements are consecutively substituted on Ni, Mn, and Ga sites, to establish the effect of positional substitution and elemental evolution. The elemental dependence of saturation magnetization, magnetocrystalline anisotropy, Curie temperature, and martensitic transformation temperatures are compared with (non-)stoichiometric Ni-Mn-Ga Heusler compounds. The observed behavior is complex and there are no clear trends of transformation temperatures as a function of the number of valence (non-bonding) electrons per atom, however, the saturation magnetization at 10K and Curie temperature seems to follow the Pauli-Slater curve. Obtained results can serve as useful rectification for the theoretical prediction of new Ni-Mn-Ga-X Heusler alloys.

The interest in the Spark Plasma Sintering (SPS) technique has continuously increased over the last few years. This article shows the possibility of the development of a SPS device used for material processing and synthesis both in both scientific and industrial applications. This work presents an example of processing Arc-Meleted (half-Heusler, cobalt triantimonide) and SHS-synthesized semiconductors (bismuth telluride) materials with SPS device. The system functionalities expansion is presented, showing the possible way of increasing the information amount obtained about SPS processes and using the SPS apparatus for conducting synthesis of materials and increasing reproducibility and accuracy of process parameters control.