Spin-like susceptibility of metallic and insulating thin films at low temperature

Abstract

Susceptibility measurements of patterned thin films at sub-K temperatures were carried out using a scanning SQUID microscope that can resolve signals corresponding to a few hundred Bohr magnetons. Several metallic and insulating thin films, even oxide-free Au films, show a paramagnetic response with a temperature dependence that indicates unpaired spins as the origin. The observed response exhibits a measurable out-of-phase component, which implies that these spins will create 1/f-like magnetic noise. The measured spin density is consistent with recent explanations of low frequency flux noise in SQUIDs and superconducting qubits in terms of spin fluctuations, and suggests that such unexpected spins may be even more ubiquitous than already indicated by earlier measurements. Our measurements set several constraints on the nature of these spins.

Journal version. 4 pages, 2 figures. See http://www.stanford.edu/group/moler/publications.html for the auxiliary document containing additional data and discussion (Ref. 15). Changes w.r.t. v1: Clarified some details, moved some technical points to auxiliary document

References in corpus (11)

• Decoherence of flux qubits due to 1/f flux noise
• Persistent currents in normal metal rings
• Model for l/f Flux Noise in SQUIDs and Qubits
• 1/f Flux Noise in Josephson Phase Qubits
• Magnetism in SQUIDs at Millikelvin Temperatures
• Microscopic origin of low frequency flux noise in Josephson circuits
• Dangling-bond spin relaxation and magnetic 1/f noise from the amorphous-semiconductor/oxide interface: Theory
• Magnetic field enhancement of superconductivity in ultra-narrow wires
• Probing Noise in Flux Qubits via Macroscopic Resonant Tunneling
• Geometrical dependence of low frequency noise in superconducting flux qubits
• Strong magnetic scattering from TiO${}_x$ adhesion layers

Cited by in corpus (12)

• Diamond surface engineering for molecular sensing with nitrogen-vacancy centers
• Scanning gradiometry with a single spin quantum magnetometer
• Quantitative evaluation of defect-models in superconducting phase qubits
• Correlated flux noise and decoherence in two inductively coupled flux qubits
• Mott transition in granular aluminum
• Surface roughness noise analysis and comprehensive noise effects on depth-dependent coherence time of NV centers in diamond
• Observation of Co-tunneling in Pairs of Coupled Flux Qubits
• Nonequilibrium Spin Noise and Noise of Susceptibility
• 1/f Noise from the Laws of Thermodynamics for Finite-Size Fluctuations
• An Ising-Glauber Spin Cluster Model for Temperature Dependent Magnetization Noise in SQUIDs
• 1/f noise in quantum nanoscience
• Design concepts for an improved integrated scanning SQUID