Enhanced Magnetocaloric Effect from Cr Substitution in Ising Lanthanide Gallium Garnets Ln3CrGa4O12 (Ln = Tb, Dy, Ho)

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Mukherjee, Paromita  ORCID logo  https://orcid.org/0000-0001-5121-6280
Dutton, SE 

A detailed study on the crystal structure and bulk magnetic properties of Cr substituted Ising type lanthanide gallium garnets Ln3CrGa4O12 (Ln = Tb, Dy, Ho) has been carried out using room temperature powder X-Ray and neutron diffraction, magnetic susceptibility, isothermal magnetisation and heat capacity measurements. The magnetocaloric effect (MCE) in Ln3CrGa4O12 is compared to that of Ln3Ga5O12. In lower magnetic fields attainable by a permanent magnet (≤2 T), Cr substitution greatly enhances the MCE by 20% for Ln = Dy and 120% for Ln = Ho compared to the unsubstituted Ln3Ga5O12. This is likely due to changes in the magnetic ground state as Cr substitution also significantly reduces the frustration in the magnetic lattice for the Ising type Ln3Ga5O12.

Cr substitution, lanthanide garnet, magnetocaloric effect
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Advanced Functional Materials
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Engineering and Physical Sciences Research Council (EP/M000524/1)
The authors acknowledge funding support from the Winton Programme for the Physics of Sustainability. Magnetic measurements were carried out using the Advanced Materials Characterization Suite, funded by EPSRC Strategic Equipment Grant EP1M00052411. Supporting data can be found at https://doi.org/10.17863/CAM.9895, neutron diffraction data can also be found at https://doi.org/10.5291/ILL-DATA.5-31-2457.Figure 7. ∆Sm per mole as a function of temperature for Ln3CrGa4O12 compared to Ln3Ga5O12 (Ln = Tb, Dy, Ho) in a field of 2 T, the inset: field dependence of ∆Sm per mole at T = 2 K – a) Ln = Tb, b) Ln = Dy, c) Ln = Ho.
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