A method for ultrasensitive magnetostriction measurement

Determination of Joule magnetostriction by the method of tensile strain measurement has a lower limit of about 10
^-6
because of error strains clue to magnetostatic forces and changes in temperature. It is shown that these disturbances can be eliminated by measuring shear strains induced in thin-walled tubes by helical magnetic fields. By a resonance method, the measurement of the magnetostriction constant can be made down to 10
^-13
.