Lanthanide contraction and magnetism in the heavy rare earth elements

Area of Science:

• Condensed Matter Physics
• Materials Science
• Solid State Chemistry

Background:

• Heavy rare earth elements possess hexagonally close packed (h.c.p.) structures and localized magnetic moments due to 4f electrons.
• Magnetic structures in these elements, often incommensurate with the crystal lattice, are linked to the Fermi surface topology.
• The dependence of magnetic structure on the c/a lattice ratio is recognized, but theoretical understanding remains incomplete.

Purpose of the Study:

• To establish a unified magnetic phase diagram for heavy rare earth elements.
• To correlate magnetic structures with specific lattice parameters (c/a ratio and unit cell volume).
• To elucidate the role of lanthanide contraction in the observed magnetic trends.

Main Methods:

• Utilized gadolinium as a representative heavy rare earth element.
• Generated a comprehensive magnetic phase diagram.
• Analyzed the relationship between lattice parameters and magnetic ordering.

Main Results:

• Developed a unified magnetic phase diagram linking heavy rare earth magnetic structures to lattice parameters.
• Confirmed the significance of the c/a ratio in determining magnetic properties.
• Identified atomic unit cell volume as a distinct factor influencing magnetic behavior, showing a trend from ferromagnetism to incommensurate ordering with decreasing volume due to lanthanide contraction.

Conclusions:

• The study provides a unified framework for understanding heavy rare earth magnetism based on lattice parameters.
• Both the c/a ratio and unit cell volume are critical determinants of magnetic structure.
• Lanthanide contraction plays a key role in the evolution of magnetic properties across the heavy rare earth series.