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Robust spin-ice freezing in magnetically frustrated Ho2GexTi2-xO7pyrochlore
Manjari Shukla1, Rajnikant Upadhyay1, Martin Tolkiehn2
1School of Materials Science and Technology, Indian Institute of Technology (Banaras Hindu University) Varanasi -221005, India.
Summary
Chemical pressure in Ho2GeTi2-xO7 pyrochlores tunes spin dynamics, weakening ferromagnetic interactions and favoring antiferromagnetic coupling. This leads to a shift in single-ion freezing but preserves the quantum tunneling spin ice behavior.
Area of Science:
- Condensed Matter Physics
- Materials Science
- Magnetism
Background:
- Spin frustrated pyrochlore oxides exhibit complex magnetic interactions.
- Holmium germanate titanate (Ho2GeTiO7) is a model system for studying spin frustration.
- Chemical pressure is a tool to tune magnetic properties in materials.
Purpose of the Study:
- To investigate the effect of chemical pressure on the spin dynamics of Ho2GeTiO7.
- To analyze the interplay between exchange and dipolar interactions under varying Ge content.
- To understand the mechanisms governing spin freezing phenomena in these materials.
Main Methods:
- High-resolution and low-temperature synchrotron X-ray diffraction for structural analysis.
- Static magnetic measurements (magnetization vs. temperature and field).
- Dynamical magnetic measurements (AC susceptibility) to probe spin dynamics.
Main Results:
- Increased chemical pressure (higher Ge content) weakens ferromagnetic interactions in Ho2GeTiO7.
- Curie-Weiss temperature decreases significantly, indicating a shift towards antiferromagnetic coupling.
- Thermally activated single-ion spin freezing shifts to lower temperatures due to altered crystal field effects, while quantum tunneling spin ice behavior remains robust.
Conclusions:
- Positive chemical pressure in Ho2GeTiO7 establishes the dominance of antiferromagnetic interactions.
- Crystal field-phonon coupling influences single-ion spin relaxation under chemical pressure.
- The 'ice rule' spin configuration, driven by quantum tunneling, is resilient to applied chemical pressure.
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