Thin Film Growth of Heavy Fermion Chiral Magnet YbNi3Al9

TL;DR

This study successfully grew thin films of the heavy fermion chiral magnet YbNi3Al9 using molecular beam epitaxy, revealing magnetic properties similar to bulk samples and demonstrating the presence of a chiral soliton lattice phase in thin films.

Contribution

First demonstration of epitaxial thin film growth of YbNi3Al9 with preserved magnetic phases and chiral soliton lattice behavior.

Findings

Resistivity shows dense Kondo behavior and magnetic ordering at 3.6 K.

Magnetoresistance indicates field-induced phase transition.

Magnetic phase diagram matches bulk crystal behavior.

Abstract

We grew thin films of a heavy fermion chiral magnet YbNi$_3$Al$_9$ by using molecular beam epitaxy. They were grown on $c$-plane sapphire substrates under ultra-high vacuum while maintaining a deposition rate at a stoichiometric ratio among Yb, Ni, and Al. The resulting thin films contain epitaxial grains with a $c$ axis parallel to the substrate surface: The YbNi$_3$Al$_9$ $c$ axis is parallel to the sapphire $b$ or $a$ axis. The temperature dependence of the resistivity exhibits a typical feature of a dense Kondo system with a broad shoulder structure at $\sim$40\,K, as well as a kink as a signature of the chiral helimagnetic ordering at 3.6\,K. These features are consistent with those previously observed in bulk samples. The shift in the kink associated with the field-induced phase transition is found in the magnetoresistance curves under a magnetic field applied in the direction perpendicular to the $c$-axis. The magnetic phase diagram well reproduces that for the bulk crystals, implying that the chiral soliton lattice phase arises under magnetic fields, even in thin films.