Power Losses in LaFe_xCo_ySi_1.1Intermetallics near the Magnetic Phase Transition

Abstract

The paper presents magnetic parameters of LaFexCoySi1.1 bulk specimens proving strong magnetocaloric eect. The main research work was oriented on measurements of the alloy's power losses according to IEC 60404 standards and validated with unbalanced bridge method and other methods. The measurements of the LaFe10.8Co1.1Si1.1 specimens were determined in the range of temperatures near the Curie temperature where the magnetocaloric eect is the strongest. Power losses were taken into account mainly for the evaluation of usefulness and eciency in the magnetic refrigeration applications. The results of presented measurements testify that the most suitable range of temperature and the best operational conditions are very close to the point of magnetic phase transition and slightly above it. It indicates that the magnetic state between the T∆Smax and Tc is more eective for the magnetic refrigeration applications due to lower power losses and high level of the isothermal changes of entropy. Operating temperature below the T∆Smax in ferromagnetic state is improper because of the increasing power losses which achieve the level of 130 mJ/kg for main frequency and decrease to 20 mJ/kg for the value of 0.1 Hz.

Scaling of Anhysteretic Curves for LaFeCoSi Alloy near the Transition Point

“…The experimental results, curves and the detailed description of the measurement setup have been discussed previously in detail in Refs. [14,15].…”

Magnetic Properties and Flux Distribution in the LaFeCoSi/FeCoV Hybrid Structure

“…In the range from 292 K to 350 K measured magnetic polarization J max in the hybrid structure drops to the value of 0.43 T while reduced polarization J max in MCM core without FM lamination does not exceed 0.03 T. The influence of the temperature on magnetic properties of the magnetocaloric compound LaFe 10.8 Co 1.1 Si 1.1 was discussed in paper [17]. The same dependences of the FM laminations in the considered temperature range can be neglected because the Curie temperature equals 1223 K, respectively.…”

“…This is the result of saturation in the MCM components and causes a significant increase in energy loss per cycle (Fig. 4b) compared to the loss in the MCM core without FM laminations [17]. Coercive field and magnetic remanence of the hybrid structure (Fig.…”

“…4a) does not depend on the frequency f mag . It also results in growth of the hysteresis loss component [17].…”

Investigations of the Magnetic Phase Transition in the LaFe_{11.14}Co_{0.66}Si_{1.1}M_{0.1} (Where M~=~Al or Ga) Alloys

“…Besides the listed compounds, Mn- [6], Co- [7], Gd- [8,9] and Fe-based [10][11][12] alloys have been intensively studied. The Fe-based alloys are relatively cheap compared to the above mentioned materials and are characterized by excellent magnetic properties [13][14][15].…”