Observation of Electromagnetic Angular Momentum within Magnetite

Abstract

A hollow cylinder of magnetite at 4 K has been subjected to the simultaneous action of constant axial magnetic field $\stackrel{\ensuremath{\rightarrow}}{\mathrm{B}}$ and low-frequency radial electric field $\stackrel{\ensuremath{\rightarrow}}{\mathrm{E}}$. The reaction torque, which appears in the magnetite as the electromagnetic angular momentum changes, has been observed for the first time. Preliminary results favor the Livens' reaction-force density $\frac{\ensuremath{-}\ensuremath{\partial}({\ensuremath{\epsilon}}_{0}\stackrel{\ensuremath{\rightarrow}}{\mathrm{E}}\ifmmode\times\else\texttimes\fi{}\stackrel{\ensuremath{\rightarrow}}{\mathrm{B}})}{\ensuremath{\partial}t}$ and contradict the alternative $\frac{\ensuremath{-}\ensuremath{\partial}({\ensuremath{\epsilon}}_{0}{\ensuremath{\mu}}_{0}\stackrel{\ensuremath{\rightarrow}}{\mathrm{E}}\ifmmode\times\else\texttimes\fi{}\stackrel{\ensuremath{\rightarrow}}{\mathrm{H}})}{\ensuremath{\partial}t}$ of Einstein and Laub which was followed by Abraham and is widely accepted by modern authors.