# Magnetic Properties of New Triangular Lattice Magnets A${_4}$B'B${_2}$O$_{12}$

## TL;DR

This study investigates the magnetic behaviors of A4B'B2O12 triangular lattice magnets, revealing how different transition metal ions and chemical pressure influence their ferromagnetic or antiferromagnetic ground states.

## Contribution

It provides new insights into how spin number and chemical pressure affect magnetic ordering in geometrically frustrated triangular lattice magnets.

## Key findings

- Co2+ and Ni2+ samples show ferromagnetic order
- Mn2+ sample exhibits antiferromagnetic order
- Chemical pressure tunes ferromagnetic transition temperature

## Abstract

The geometrically frustrated two dimensional triangular lattice magnets A${_4}$B'B${_2}$O$_{12}$ (A = Ba, Sr, La; B' = Co, Ni, Mn; B = W, Re) have been studied by x-ray diffraction, AC and DC susceptibilities, powder neutron diffraction, and specific heat measurements. The results reveal that (i) the samples containing Co$^{2+}$ (effective spin-1/2) and Ni$^{2+}$ (spin-1) ions with small spin numbers exhibit ferromagnetic (FM) ordering while the sample containing Mn$^{2+}$ (spin-5/2) ions with a large spin number exhibits antiferromagnetic (AFM) ordering. We ascribe these spin number manipulated ground states to the competition between the AFM B'-O-O-B' and FM B'-O-B-O-B' superexchange interactions; (ii) the chemical pressure introduced into the Co containing samples through the replacement of different size ions on the A site finely tunes the FM ordering temperature of the system. We attribute this effect to the modification of the FM interaction strength induced by the change of the O-B-O angle through chemical pressure.