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OBJECTIVES

Efficient Magnetic Refrigeration Using Matrix Embedded Iron Nanoparticles

Kaushik Sarkar 1, Jacob Som1, Manosi Roy1, Christian Binek2, Dhananjay Kumar 1

1Department of Mechanical Engineering, North Carolina A&T State University, Greensboro

2Department of Physics and Astronomy, University of Nebraska-Lincoln

ACKNOWLEDGEMENTS

  • This work was supported by the National Science Foundation (NSF) through the MRSEC (grant No. DMR-1420645) and PREM (grant No. DMR-2122067).
  • We also like to thank NSF-MRI (Grant No. CMMI-1040290) for Pulsed Laser Deposition facility at NCA&T State University.

FUTURE STUDIES

BACKGROUND

PLD: BOTTOM-UP THIN FILM FABRICATION METHOD

EXPERIMENTAL SETUP

DATA AND RESULTS

The objective is to understand the fundamentals of nanoscale magnetocaloric phenomenon and to develop magnetic refrigeration devices

MAGNETIC PROPERTIES

CONCLUSIONS

  • We studied structural, magnetic, and magnetocaloric properties of Fe nanoparticles embedded in TiN thin film grown on c-plane sapphire substrate using the PLD technique.
  • A maximum inverse MCE with an entropy change of 1.46 × 103 J/K m3 at 10 K and a forward MCE with an entropy change of 4.18 × 103 J/K m3 at 300 K are obtained for the magnetic field of 0.075 T and 3 T, respectively
  • Efficient magnetocaloric effect is observed for Fe (NP)-TiN multilayer system which holds the promise for its use in magnetic refrigeration.
  • A comparative study with different Fe nanoparticle sizes with appropriate spacer layer.
  • Measurement of MCE by varying the different layer thickness for Fe-TiN multilayer thin films.

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11th Annual COE Graduate Poster Presentation Competition

  • Magnetocaloric effect (MCE) is defined as the change of temperature or magnetic entropy of magnetic materials when it is subjected to an external field adiabatically.
  • Our aim is to develop a low-cost and sustainable material system exhibiting MCE.

Figure 2: Pulsed Laser Deposition Technique

TEANSMISSION ELECTRON MICROSCOPY

MAGNETOCALORIC EFFECT (MCE)

DATA AND RESULTS

DATA AND RESULTS

STRUCTURAL & MORPHOLOGICAL CHARACTERIZATION

  • XRD study suggests that TiN films are textured with respect to (111) planes. There are no visible peaks corresponding to Fe particles due to very low volume fraction (~0.1%) embedded in the TiN film matrix.
  • SEM image shows that iron nanoparticles are dispersed throughout the TiN film surface.
  • The average size of the nanoparticles is calculated as ~15 nm by analyzing the AFM data.

 

  • The ZFC M-T curves at various fields were differentiated to obtain the change in magnetization with respect to temperature over the magnetic field range 0.0025 T- 3 T.
  • A maximum inverse MCE with an entropy change of 1.46 × 103 J/K m3 at 10 K and a forward MCE with an entropy change of 4.18 × 103 J/K m3 at 300 K are obtained for the magnetic field of 0.075 T and 3 T, respectively.

Figure 1: Magnetocaloric effect

Figure 4: (a) X-ray diffraction pattern of 6 × Fe-TiN multilayer sample grown on a sapphire substrate at 500˚ C. (b) SEM image of Fe-TiN thin film sample, (c) Representative AFM surface topography of 0.5 × 0.5 μm2 scan

The size of the Fe nanoparticles and TiN layers were controlled by setting a total of 150 pulses for Fe layers and 800 pulses of TiN layer .

Figure 5: (a) Bright-field TEM image showing the three distinct zones, Fe-TiN thin film of approximately 60 nm thickness is sandwiched between a sapphire substrate and protective Pt layer, (b) HRTEM image showing the polycrystalline nature of Fe-TiN thin film with corresponding FFT pattern (inset) corroborating the polycrystallinity of TiN, (c) High angle annular dark field (HAADF) image, and (d) elemental map showing the alternating layers of Fe and TiN.

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  • Average temperature entropy change and refrigerant capacity is calculated and plotted in figure 8.
  • Both the TEC (10) and RC values increase with an increase in the magnetic field, but at higher fields of 2 T and 3 T, the TEC (10) curve flattens out slightly.
  • The TEC (10) and RC reach the maximum values of 3.38 × 103 J/m3 and 7.4 × 105 J/m3, respectively at 3T.

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Figure 6: (a) Magnetic field dependence of magnetization M(H) data at various temperatures from 10 K to 300 K (b) Magnetization plotted against applied field (H) over temperature (K) (c) Variation of coercivity with temperature for Fe–TiN samples (d) Blocking temperature (TB) at different applied fields for Fe-TiN multilayer grown on a sapphire substrate.

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Figure 7: (a) Temperature dependence of the magnetic-entropy change ΔS obtained under various fields from (a) 0.0025 to 0.075 T and (b) 0.1 to 3 T

Figure 8: Field dependence of TEC and RC at applied field from 0.1-3T.

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Cross-Disciplinary Research Area: Magnetism

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