New insight into magneto-structural phase transitions in layered TbMn₂Ge₂-based compounds

Area of Science:

• Condensed Matter Physics
• Materials Science
• Magnetism

Background:

• The Tb$_{1-x}$Y$_{x}$Mn$_{2}$Ge$_{2}$ series exhibits complex magnetic behavior.
• Understanding the influence of Y substitution on magnetic transitions is crucial for materials design.

Purpose of the Study:

• To investigate the magnetic phase transitions in Tb$_{1-x}$Y$_{x}$Mn$_{2}$Ge$_{2}$ compounds (x = 0, 0.1, 0.2).
• To analyze the effect of Yttrium (Y) substitution for Terbium (Tb) on magnetic transition temperatures and magnetocaloric properties.

Main Methods:

• Synthesis and characterization of Tb$_{1-x}$Y$_{x}$Mn$_{2}$Ge$_{2}$ compounds.
• Temperature-dependent magnetic susceptibility measurements to determine magnetic transition temperatures (T$_{N}^{inter}$ and T$_{C}^{inter}$).
• Analysis of magnet-volume effects and magnetic entropy changes.

Main Results:

• Two magnetic phase transitions were observed: paramagnetic to antiferromagnetic interlayer at T$_{N}^{inter}$ and antiferromagnetic to ferrimagnetic interlayer at T$_{C}^{inter}$ with decreasing temperature.
• T$_{N}^{inter}$ showed a slight increase with Y substitution, while T$_{C}^{inter}$ significantly decreased from 97.5 K (x=0) to 74.6 K (x=0.2).
• A strong anisotropic magnet-volume effect was detected around T$_{C}^{inter}$, with maximum magnetic entropy changes of up to 11.9 J kg$^{-1}$ K$^{-1}$ for x=0.1.

Conclusions:

• Yttrium substitution effectively reduces the ferrimagnetic transition temperature in Tb$_{1-x}$Y$_{x}$Mn$_{2}$Ge$_{2}$ due to chemical pressure and magnetic dilution.
• The observed magnet-volume effect and magnetocaloric properties highlight the potential of these materials for magnetic cooling applications.