We present an investigation involving the tuning of the magnetic, magnetocaloric, and room-temperature structural properties of Mn65-xGa17C18+x (0 <= x <= 4) compounds prepared using a high-energy ball milling (HEBM) technique. This study indicates that the crystal structure of all the compounds can be described as an anti-perovskite cubic structure with the Pm-3m space group and the crystal cell volume decreases with increasing carbon concentration. The system shows a first-order structural phase transition at a temperature T = T-M between two cubic phases having different magnetic structures. The phases are characterized by antiferromagnetic (AFM) and ferromagnetic (FM) -like behavior at low (T < T-M) and high (T-M > T) temperature regions, respectively. A suppression of the AFM phase was observed with increasing C concentration. The temperature-induced first-order transitions (FOTs) were found to possess a small thermal hysteresis in the magnetization (similar to 2-3 K) in an applied magnetic field of H = 50 kOe. Magnetic entropy changes estimated from isothermal magnetization curves indicate that the largest value of the magnetic entropy change of |Delta S-M| = 2.1 J kg(-1) K-1 for x = 4 with Delta H = 50 kOe, with a relative cooling power (RCP) of similar to 190 J kg(-1).Thus high-energy ball milling (HEBM), a scalable technique, has been demonstrated as a viable method to synthesize magnetocaloric materials with substantial RCP values.

We present results on the structural and magnetic properties of the B-doped Mn60Ga20C20-xBx system with x = 0, 1, 2, 3, 4 and 5. A ball milling technique followed by pressing the components, and annealing under an ultra-high purity argon atmosphere for 2 h was employed to fabricate the samples. According to the XRD diffraction data, all samples can be described as single-phase compounds (i.e., the Mn3Ga cubic phase in the Pm-3 m space group) where impurity phases did not exceed 5 %. The compounds with x < 5 show similar physical behaviors as the parent, Mn3Ga2C2, which can be generally characterized by a low temperature transition from low to high magnetization states. High boron concentrations were found to completely suppress the antiferromagnetic state. The (x-T-C) phase diagram at 10 K has been constructed and discussed. The magnetocaloric measurements result in magnetic entropy changes of 3.0 Jkg(-1)k(-1) at 5 T and Delta T-ad by direct measurement of about 0.8 K at 1.8 T.

The magnetooptical spectra of the transverse Kerr effect of (CoFeZr)(x)(Al2O3)(1-x) nanocomposites are calculated within the framework of the symmetrized Maxwell-Garnett (SMG) approximation. The quasi-classical size effect and the size distribution of the granules were taken into account. The calculation results for the spectral range 0.5-3.5 eV and different concentrations of the magnetic component are in semi-quantitative agreement with the experimental data. A possible reason for the existing discrepancy is the difference between the optical and magneto-optical parameters of ferromagnetic granules from those corresponding for bulk samples.

We present an overview of the factors affecting soft magnetic properties and giant magnetoimpedance (GMI) effect of thin amorphous wires. Low coercivity and high GMI effect have been observed in as-prepared Co-rich microwires. We showed that the magnetoelastic anisotropy is one of the most important parameters that determines the magnetic softness and GMI effect of glass-coated microwires, and annealing can be very effective for manipulation of the magnetic properties of amorphous ferromagnetic glass-coated microwires. After annealing of Co-rich microwires, we can observe the transformation of inclined hysteresis loops to rectangle and coexistence of fast magnetization switching and GMI effect in the same sample. We demonstrated that the switching field value of microwires can be tailored by annealing in the range from 4 to 200 A/m. On the other hand in Fe-rich FeCuNbSiB microwires after appropriate annealing, we observed considerable magnetic softening and GMI effect enhancement.

We studied the effect of annealing on magneto-transport, magnetic, and structural properties of Cu100−x Co x (x = 5, 10, 20) glass-coated microwires prepared using the Taylor-Ulitovsky technique. Both as-prepared and annealed samples exhibit magnetoresistance effect. We observed a Kondo-like effect in as-prepared and annealed Cu95Co5 microwire and a significant increase of the giant magnetoresistance (GMR) in all studied Co-Cu after annealing. The origin of GMR effect and Kondo-like behavior is discussed considering structural changes of the annealed samples.

We report on magnetic, transport and structural properties of Co-x-Cu100-x (5 <= x <= 30) and Fe37Cu63 glass-coated microwires prepared by the Taylor-Ulitovsky method. The objective of the reported work is to develop a novel functional materials exhibiting giant magnetoresistance (GMR). For Co-Cu microwires with x = 5 we observed the resistivity minimum at 40 K associated with the Kondo-like behaviour but magnetoresistance is small. For x = 10 magnetoresistance reaches 9 % at low temperatures. Temperature dependence of susceptibility shows considerable difference for x > 10 and x <= 10 attributed to the presence of small Co grains embedded in the Cu matrix for x >= 10. By X-ray diffraction we found, that the structure of CoxCu100-x microwires for x = 10 is granular consisting of two phases: fcc Cu appearing in all the samples and fcc alpha-Co presented only in microwires with higher Co content. Structure of Fe37Cu63 microwires consists of Cu nanograins with average grain size of around 40 nm and alpha-Fe nanocrystals with average grain size ranging between 6 and 45 nm depending on samples geometry. These microwires also exhibit GMR (up to 7.5 % at 5 K).

In this chapter, we will survey early and recent experimental results on magnetic properties of dilute magnetic oxide semiconductors, focusing on TiO2-δ:Co and TiO2-δ:V. Room temperature ferromagnetism was observed in both types of thin film samples fabricated by RF sputtering, but their magnetic properties appeared to be quite different. Magnetic moments in case of TiO2-δ:Co are mostly associated with local polarization of Co ions and induced defects. There is an evidence of intrinsic ferromagnetism in the case of low Co content (<1 at.%). Room temperature ferromagnetism was observed in TiO2-δ:V at V content from 3 up to 18 at.% in the whole resistivity range from 10−3 up to 106 Ω cm. Positron annihilation spectroscopy revealed a correlation between magnetization and concentration of the negatively charged defects in TiO2-δ:V thin films. The origin of room temperature ferromagnetism in these systems is discussed. Besides, the recent research findings in ZnO-based magnetic semiconductors are briefly discussed with focus on defect-induced ferromagnetism.

A lot of factors limit possible applications of magnetic nanoparticles in medicine for drug delivery and magnetic hyperthermia therefore it is of primary importance to understand influence of classical and quantum-size effects, surface layers, interparticle distance, shape of nanoparticles on their magnetic properties. Magnetic nanogranular thin films, known also as nanocomposites, can be considered as a convenient model for such investigations as it is possible to tune easily many of mentioned above parameters by varying of the fabrication conditions. The ion-beam sputtering technique has been developed to prepare “amorphous ferromagnetic metal-insulator” nanocomposites with different concentration and parameters simultaneously in one technological cycle. This feature is achieved by using of a composite target (consisting of a metal and dielectric parts) with an asymmetric arrangement of the dielectric parts on the metal base. Influence of sputtering conditions and post-fabrication treatment on structural, magnetic, electrical and magnetotransport properties of magnetic nanocomposites in a wide range of metal volume fraction and distance between magnetic nanoparticles is being discussed.

In this review, we will survey recent experimental results on magnetic, magnetocaloric, magnetotransport, and magneto-optical properties of Ni–Mn–In-based Heusler alloys in bulk polycrystalline samples, melt-spun ribbons, and glass-coated microwires. These ternary Ni–Mn–In and doped, quaternary alloys comprise a novel class of multifunctional magnetic materials with exceptional properties related to the magnetostructural martensitic transformation. We will focus on recent developments that have led to a better understanding of properties that are promising for applications, possible routes for improvements, and the identification of unsolved problems.

The trend of big data in Fig.1 creates the big progress of sensors towards to like bio sensors. Like bio sensors must have high performance in super high resolution, micro size, low power consumption, real-time, low cost and mass production. The like bio sensors must be archived by combination of sensor innovation and the sensor fusion smart system. In the field of magnetic sensors the developments of high resolution micro size magnetic sensors and their new applications such as wearable computer in Fig.2, medical applications in Fig.3, automotive driving systems, smart grid has been dramatically progressed. MI sensor which consists of amorphous wire and MEMS coil must be most promising super high resolution micro size magnetic sensors. Recently the remarkable progress on MI sensor improved by pulse stimulation from MHz to GHz and fine pithed MEMS coil from 30 μm to 5μm in Fig.4 which gives the 100 times increase in sensitivity compared to that of MHz type MI sensor is reported. I propose GHz type MI sensor as GHz-spin rotation sensor (GSR sensor1)). This GSR sensor must measure the earth magnetism easily and apply to gyro compass which is used as motion sensor for wearable computer. Moreover it can detect bio magnetism of Pico tesla level and apply to heart magnetic cardiogram and magnetoencephalography. The keynote speech will introduce the recent developments in super high resolution micro size magnetic sensors and their high light applications challenged in Silicon Valley.

We report the magnetic and magneto-optical (MO) properties of the Heusler Ni43.7Mn43.6In12.7 alloy ribbon in martensitic and austenitic states. The samples were produced by rapid solidification using the melt-spinning technique. The difference between the transformation temperatures obtained from magnetization and transverse Kerr effect (TKE) measurements shows that the chemical composition and/or microstructure are not identical in the bulk and at the ribbon surface. The TKE spectra profile in the spectral energy range of 0.5-3.5 eV does not change significantly at the martensitic transformation that indicates on a very similar electronic structure in martensitic and austenitic states.

Transverse Kerr effect (TKE) was used to study magneto-optical (MO) properties of Ni45Mn36.7In13.3Co5 (at.%) single crystals. A single crystalline ingot of such composition was grown by the Czochralski method. One series of samples was quenched into cold water (WQ) and the other series after quenching was heated at 770 K for 20 min and slowly cooled to assure a complete atomic order (SC). Accordingly to differential scanning calorimetry (DSC), magnetic and magneto-optical (MO) measurements, WQ samples exhibit well-defined martensitic transition (MT), but the SC samples do not show MT. It is found that TKE for WQ samples shows the following features (i) MO signal is well pronounced far below the martensitic transition in spite of a weak magnetization of martensitic phase; (ii) the characteristic temperatures of martensitic transition differ from those for the bulk and depend on annealing conditions; (iii) MO spectra profile do not change significantly during the martensitic transition and is similar but not identical with that for Ni50Mn35In15 thin films and Ni43.7Mn43.6In12.7 ribbons measured before; (iv) MO signal is anisotropic.

Abstract We report on the magnetic, transport and structural properties of Cox-Cu100-x (5≤x≤40) glass-coated microwires. For x=5 we observed the resistivity minimum at 40 K associated with the Kondo effect. For x ? 10 we observed considerable magnetoresistance effect. Temperature dependence of susceptibility show considerable difference for x>10 and x≤ 10 attributed to the presence of small Co grains embedded in the Cu matrix for x? 10. Using X-ray diffraction we found, that the structure of Cox-Cu100-x microwires x ? 10 is granular consisting of two phases: fcc Cu appearing in all the samples and fcc α-Co presented only in microwires with higher Co content.

We have studied magnetic and structural properties of the composite microwires consisted of the metallic core and the outer glass shell. Nominal chemical composition of the core was Ni49.5Mn25.4Ga25.1, its diameter was 13.2 μm, and the total diameter of the glass-covered microwires was 26.4 μm. We have found out that at room temperature the core of the as-cast microwires was composed by two phases with tetragonal I4/mmm and cubic Fm3m crystal structures, but annealing rendered it single phase. Measurements of the magnetic properties have demonstrated substantial growth of the magnetic anisotropy with cooling, which we have attributed to the phase transition from the room-temperature austenitic to the low-temperature martensitic state. Magnetic easy axis was found to be perpendicular to the axis of the microwires at low temperatures. We believe that it is a result of the crystallographic texture induced in the martensite by high internal stress characteristic of the glass-covered magnetic microwires. Though rearrangement of the martensitic microstructure under external pressure was previously observed in the single crystal Ni2MnGa samples, in composite materials this effect is new and can be potentially useful for the applications.

Magnetic, transport and structural properties of granular Co-x-Cu100-x (5 < x < 40 at.%) glass-coated microwires were studied. Co-Cu microwires exhibited giant magnetoresistance (GMR) effect. For x=5% we observed the resistivity minimum at 40 K associated with the Kondo effect. For x > 10 partial evidences of granular structure have been observed. For x >= 30 anisotropic contribution to GMR has been observed giving rise to nonmonotonic dependence of GMR on the field. Temperature dependence of magnetization measured during a cooling regime without external magnetic field and in the presence of the field shows considerable difference at low temperatures, being attributed to the presence of small Co grains embedded in the Cu matrix. By X-ray diffraction we found, that the structure of the metallic nucleus is granular consisting of two phases: fcc Cu appearing in all the samples and fcc alpha-Co presented only in microwires with higher Co content. For low Co content (x <= 10%) X-ray diffraction technique indicates that Co atoms are distributed within the Cu crystals. The quantity and the crystallite size of the formed phases strongly depend on the geometry of the microwire. The structure, magnetic and transport propertieswere affected by the glass coating inducing the internal stresses and affecting the quenching rate. (C) 2013 Elsevier B.V. All rights reserved.

We present recent experimental results on the structural, electrical, magnetic, and magneto-optical properties of Mn-implanted Si and Co-doped TiO(2-delta) magnetic oxides. Si wafers, both n- and p-type, with high and low resistivity, were used as the starting materials for implantation with Mn ions at the fluencies up to 5 x 10(16) cm(-2). The saturation magnetization was found to show the lack of any regular dependence on the Si conductivity type, type of impurity and the short post-implantation annealing. According to XMCD Mn impurity in Si does not bear any appreciable magnetic moment at room temperature. The obtained results indicate that above room temperature ferromagnetism in Mn-implanted Si originates not from Mn impurity but rather from structural defects in Si. The TiO(2-delta):Co thin films were deposited on LaAlO3 (001) substrates by magnetron sputtering in the argon-oxygen atmosphere at oxygen partial pressure of 2 x 10(-6)-2 x 10(-4) Torr. The obtained transverse Kerr effect spectra at the visible and XMCD spectra indicate on intrinsic room temperature ferromagnetism in TiO(2-delta):Co thin films at low (< 1%) volume fraction of Co.

We report magneto-optical spectra of the Heusler bulk alloys Ni-Mn-In, thin films Ni-Mn-Ga, microwires Ni-Mn-In and Ni-Mn-Ga in martensitic and austenitic states. Transversal Kerr effect (TKE) was studied at an angle of light incidence of 68° with respect to the sample plane, in the energy range 0.5 eV < E < 4.0 eV, at 50 350 K temperatures, and in magnetic fields up to 3.5 kOe. The TKE spectra profile does not change too much at martensitic transformation in Ni2MnGa thin films, only magnitudes of characteristic maxima decrease. The magneto-optical response of Ni2MnGa microwires is very similar to that for Ni2MnGa thin films. For most of studied bulk samples, the TKE signal is very weak (about 10-5), about two orders of magnitude smaller than for thin films, and in many cases could not be detected at all. It indicates the strong dependence of the magneto-optical response of Heusler alloys on the quality of optically or electrochemically polished surfaces and their microstructure.

V. Zhukova, M Ilyn, C. Garcia, R. Varga, J. J. del Val, A. Granovskyand A. Zhukov Dpto. de Física de Materiales, Fac. Químicas, UPV/EHU, 20018, San Sebastián, Spain Bogazici Univ, Dept Phys, TR-34342 Istanbul, Turkey Inst. Phys., Fac..Sci., UPJS, Park Angelinum 9, Kosice, Slovakia Moscow State University, Moscow, 119991, Russian Federation IKERBASQUE, Basque Foundation for Science, 48011 Bilbao, Spain valentina.zhukova@ehu.es