Ultralow-field nuclear magnetic resonance of liquids confined in ferromagnetic and paramagnetic materials

A nuclear magnetic resonance (NMR) procedure is used to measure weak magnetic fields in the vicinity of dilute ferromagnetic and/or paramagnetic materials. By detecting 1H Larmor precession in common solvents at extremely low frequencies (<50 Hz), the magnetic field produced by remanent magnetization of the material is measured by NMR to a precision of <1 nT. In one example, the technique is used to quantify the magnitude and direction of remanent magnetization in a common aluminum alloy. In another example, a 1H NMR linewidth <1 Hz is demonstrated for liquid decane (n-C10H22) embedded inside a mesoporous silica matrix, despite the high concentration of paramagnetic cobalt sites that produce magnetic susceptibility gradients in the system. Application to systems of industrial relevance is discussed.