Magnetic excitations in the metallic single-layer Ruthenates Ca(2-x)Sr(x)RuO(4) studied by inelastic neutron scattering

TL;DR

This study uses inelastic neutron scattering to analyze magnetic excitations in Ca(2-x)Sr(x)RuO(4), revealing the coexistence and competition of ferromagnetic and incommensurate antiferromagnetic fluctuations across different compositions.

Contribution

It provides a comprehensive analysis of magnetic correlations in Ca(2-x)Sr(x)RuO(4) near the Mott transition, highlighting the interplay of different magnetic fluctuations.

Findings

Ferromagnetic fluctuations are strong in Ca1.38Sr0.62RuO4 at low energy.

Incommensurate fluctuations are present across the series.

Magnetic field can induce ferromagnetic modes in low-concentration samples.

Abstract

By inelastic neutron scattering, we have analyzed the magnetic correlations in the paramagnetic metallic region of the series Ca(2-x)Sr(x)RuO(4), 0.2<=x<=0.62. We find different contributions that correspond to 2D ferromagnetic fluctuations and to fluctuations at incommensurate wave vectors (0.11,0,0), (0.26,0,0) and (0.3,0.3,0). These components constitute the measured response as function of the Sr-concentration x, of the magnetic field and of the temperature. A generic model is applicable to metallic Ca(2-x)Sr(x)RuO(4) close to the Mott transition, in spite of their strongly varying physical properties. The amplitude, characteristic energy and width of the incommensurate components vary only little as function of x, but the ferromagnetic component depends sensitively on concentration, temperature and magnetic field. While ferromagnetic fluctuations are very strong in Ca1.38Sr0.62RuO4 with a low characteristic energy of 0.2 meV at T=1.5 K, they are strongly suppressed in Ca1.8Sr0.2RuO4, but reappear upon the application of a magnetic field and form a magnon mode above the metamagnetic transition. The inelastic neutron scattering results document how the competition between ferromagnetic and incommensurate antiferromagnetic instabilities governs the physics of this system.