Correlation of Microstructure with Hard Magnetic Properties of Glass-Coated MnBi Microwires
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MRS Advances © 2018 Materials Research Society DOI: 10.1557/adv.2018.664
Correlation of Microstructure with Hard Magnetic Properties of Glass-Coated MnBi Microwires J. Zamora1, 2,*, I. Betancourt 1, A. Jiménez2, R. Pérez del Real2 and M. Vázquez2 1 Departamento de Materiales Metálicos y Cerámicos, Instituto de Investigaciones en Materiales, Universidad Nacional Autónoma de México, Ciudad de México, CP 04510. Mexico.
2
Instituto de Ciencia de Materiales de Madrid, CSIC, Sor Juana Inés de la Cruz 3, 28049 Madrid, Spain.
*Corresponding author. E-mail: [email protected]
ABSTRACT
In this work, we study the hard-magnetic properties and its influence on the microstructure of MnBi-based glass-coated microwires obtained by Taylor-Ulitovsky process, as well as their magnetic and thermal dependence in the range of 200 K-360 K. We obtained glass-coated microwires pieces trough of the Taylor-Ulitovsky process. Glass-coated microwires exhibited the formation of Low-Temperature Intermetallic Phase (LTIP)-MnBi, as confirmed by scanning electron microscopy (SEM). Energy Dispersive Spectroscopy (EDS) elemental chemical composition analysis showed LTIP regions interspersed within Bi- and Mn-rich areas. Magnetic properties were determined by vibrating sample magnetometry (VSM), for which a considerable intrinsic coercivity field (iHc) up to 6000 Oe at 360 K, together with a saturation magnetization (Ms) of 57.49 emu/cm3. Therefore, this combination of properties renders LTIP is a promising precursor with potential for applications at high temperatures.
INTRODUCTION The development of magnetic alloys that can be fabricated wire-shaped is through by two different methods: i) In-rotating-water-quenching production technique with diameters in the range 100-200 ȝm [1] and ii) the Taylor-Ulitovsky process that enables to fabricate microwires with a metallic nucleus with diameter ranging 0.1-40 ȝm and an insulating coating of pyrex glass 2-20 ȝm thick [2], which have been intensively studied due to their remarkable soft magnetic behavior, characterized by small coercivity
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values (Hc < 1 Oe), high magnetic permeability (> 10 000) and vanishing magnetocrystalline anisotropy (K1§0 for amorphous alloys), as well as properties of practical interest such as magnetomechanical and giant magnetoimpedance effects [3-5]. The main compositions fabricated by mean of this technique are transition metals (Fe, Co, Ni) and metalloids like B and Si. Up to now, glass-coated microwires with hard magnetic behavior (coercivity values over 100 Oe) have not yet been studied in detail. On another hand, search for new hard magnetic alloys rare earth-free has aroused a significant interest in recent years due to the possibility for developing competitive permanent magnets alternative to rare earth-based magnets
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