Larmor Frequency in Heterogeneous Media

TL;DR

This paper investigates the Larmor frequency shift in porous media with heterogeneous magnetic susceptibility, considering arbitrary matrix geometries and fast diffusion, to understand local magnetic field variations in NMR studies.

Contribution

It introduces a theoretical framework for analyzing Larmor frequency shifts caused by anisotropic susceptibility in complex porous structures with arbitrary geometry.

Findings

Derived a general expression for frequency shifts in heterogeneous media

Showed the impact of matrix anisotropy on local magnetic fields

Applicable to a wide range of porous media with arbitrary shapes

Abstract

The Larmor frequency shift is found in porous media consisting of NMR-reporting fluid filling a connected pore within an NMR-invisible matrix for the case of fast diffusion in the fluid. The matrix material has a distinct location-independent anisotropic magnetic susceptibility tensor that induces a heterogeneous microscopic magnetic field when exposed to the strong main field of an NMR device. Aside from the connectivity of the pore, the matrix geometry is arbitrary.