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Chemical substitution is one of the most efficient tools to tune and optimize magnetic and magnetocaloric properties of the giant magnetocaloric materials. In particular, Indium substitutions could be useful both for tuning properties of these interesting intermetallic materials and to unveil their local-scale behavior across the magnetostructural transition via hyperfine techniques. Hence, in order to investigate the effect of Indium additions on the crystal structure, micro-structure, magnetic and magnetocaloric properties, a series of In-containing samples derived from the base Gd5Si1.2Ge2.8 stoichiometry were prepared. The major findings are that while In is insoluble in the 5: 4 phase, it will instead promote the emergence of the impurity 5: 3 phase and segregates into this phase. Hence, In leads to major crystallographic changes, which enhance atomic disorder and disrupt the Si to Ge ratio in the 5: 4 phase. Subsequently, a higher 5: 4 unit cell volume and a lower magnetic ordering temperature are found in the In-substituted samples. Finally, the magnetocaloric properties of the In-substituted samples reveal a detrimental effect on the maximum magnetic entropy change.

A generalized procedure for the in situ application of magnetic fields by means of the excitation of the objective lens for magnetic imaging experiments in Lorentz microscopy and electron holography is quantitatively described. A protocol for applying magnetic fields with arbitrary in-plane magnitude and orientation is presented, and a freeware script for Digital Micrograph¿ is provided to assist the operation of the microscope. Moreover, a method to accurately reconstruct hysteresis loops is detailed. We show that the out-of-plane component of the magnetic field cannot be always neglected when performing quantitative measurements of the local magnetization. Several examples are shown to demonstrate the accuracy and functionality of the methods.

A systematic set of annealings on arc-melted synthesized Gd 5Si 2Ge 2 sample was performed. Through powder X-ray diffraction (XRD) and magnetometry measurements we monitored the effect of varying the annealing time with constant temperature (T = 1473 K) on the formation of the monoclinic (M) crystallographic phase fraction, which is the one responsible for the giant magnetocaloric effect (GMCE) in this compound. The conversion of the orthorhombic O(I) crystallographic phase into M was achieved, resulting in a significant increase of the M mass fraction. Such conversion led to a change in the magnetic transition nature, evolving from a second to a first order transition for the as-cast and annealed samples, respectively. An optimal annealing time range for the M phase conversion was identified to be within 80-120 min at T = 1473 K followed by a rapid quenching to liquid N 2. Furthermore, an increase up to ∼50 of the magnetocaloric effect was obtained for the sample annealed during 120 min. © 2012 Elsevier B.V. All rights reserved.

We report the structural and magnetotransportproperties of three 300-nm-thick Bithinfilmsgrown on Si (0 0 1) substrates by means of thermalevaporation using different buffer layer (175-nm-thick Si3N4, highly resistive Si and 800-nm-thick SiO2, respectively). X-ray diffraction (XRD) and scanning electron microscopy (SEM) indicate that the Bifilms are polycrystalline with the grains preferentially oriented along the trigonal-axis [0 0 1]. The Bifilm evaporated on SiO2 presents the highest crystallinity which reflects on a higher magnetoresistance value (120% at room temperature and 160% at 2 K and 90 kOe), whereas the lowest magnetoresistance value is found for the Bifilm evaporated on Si3N4 (90% at room temperature and 140% at 2 K and 90 kOe). The magnetic field dependence of the Hall resistivity indicates the presence of both electrons and holes whose contributions strongly depend on the temperature. As a function of temperature, a significant enhancement of the hall resistivity is found below 150 K. Interestingly, the MR values show an enhancement at the same temperature, which indicates changes in the carrier densities and mobilities below 150 K.