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technical paper
Study of the magnetostructural transition in critical element free Mn1
Magnetocaloric materials are researched as promising alternatives to conventional gas compression technologies for heat conversion. Within the known magnetocaloric
materials, the MM'X system is promising as it features a strong first order magnetostructural transition (MST) enabled by partial substitution of M, M' and X sites, where M and M' are
transition metals and X is a p-block element in orthorhombic/hexagonal structures1. Commonly used intermetallics (MnNiGe, MnCoGe 2,3) employ Ge and Co, which are critical for
their applications in electronics, and cathode materials for batteries, respectively. In the present study, Fe and Al substitutions inside a MnNiSi-based intermetallic induce a MST without
critical or expensive elements. All alloys have been synthesized by arc melting, and heat treated followed by quenching. By convenient substitution, the studied Mn1-xNi1-xFe2xSi0.95Al0.05
alloys exhibit Curie temperatures around room-temperature, which were captured by Vibrating Sample Magnetometry (VSM) as well as In-field differential scanning calorimetry (DSC)
4. The VSM magnetization over temperature data in the Mn0.69Ni0.69Fe0.62Si0.95Al0.05 sample with applied field μ0H = 1 T shown in Fig. 1 displays an abrupt variation of magnetization
with temperature, where the derivatives of magnetization exhibit a minimum between 279 and 290 K during cooling and heating, respectively. From the VSM measurements, what can be
thought of as a single-phase transition due to a single derivative minimum can be elucidated with the use of a 1K/min heating/cooling rate in the DSC. In fact, this MST is a convolution of
different transitions all close to one another, as shown during the cooling protocol in Fig. 2 from in-field DSC data with 1 T applied field. The main article will investigate the cause of such
distribution of transitions and its effect on the isothermal entropy change during heating and cooling transformations, as evaluated by a concurrent VSM and DSC study.
References:
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