Strongly Enhanced Magnetic Fluctuations in a Heavy-mass Layered Ruthenate

TL;DR

This study reveals strongly enhanced magnetic fluctuations in Ca$_{2-x}$Sr$_x$RuO$_4$ with heavy-mass behavior, linked to a magnetic instability and the active $eta$-band, providing insights into its unusual magnetic and electronic properties.

Contribution

It demonstrates the presence of significant magnetic fluctuations in Ca$_{2-x}$Sr$_x$RuO$_4$ and connects these to the $eta$-band and heavy-mass behavior, highlighting a magnetic instability.

Findings

Enhanced magnetic fluctuations around incommensurate wave vector (0.22,0,0)

Fluctuations show no correlation along c-axis and are broad in-plane

Magnetic fluctuations account for high specific heat and susceptibility

Abstract

We have studied the magnetic excitations in Ca$_{2-x}$Sr$_x$RuO$_4$, x=0.52 and 0.62, which exhibit an anomalous high susceptibility and heavy mass Fermi liquid behavior. Our inelastic neutron scattering experiments reveal strongly enhanced magnetic fluctuations around an incommensurate wave vector (0.22,0,0) pointing to a magnetic instability. The magnetic fluctuations show no correlation in c-direction and also along the RuO$_2$-planes the signal is extremely broad, $\Delta q =0.45$ \AA$^{-1}$. These fluctuations can quantitatively account for the high specific heat coefficient and relate to the high macroscopic susceptibility. The magnetic scattering is attributed to the $\gamma$-band, the active band for spin triplet superconductivity in Sr$_2$RuO$_4$.