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The pinning induced magnetostriction in an isotropic superconductor was calculated for different sample shapes. We analyzed some special shapes for which the solution can be found analytically. The magnetostriction of a finite slab was considered. In order to determine the influence of demagnetization effects, the pinning induced magnetostriction of an infinitely long and thin strip was calculated. A simple, approximate formula can be used in particular cases to analyze the magnetostriction induced by pinning forces. In this formula the magnetostriction of a sample is connected directly with its magnetization. We also present some experimental results on high temperature superconductors which are analyzed in frames of the developed theory.

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We have studied magnetostriction in single crystalline La 1.85 Sr 0.15 CuO 4 using the strain gauge technique in magnetic fields up to 12 T at temperatures 4.2 K < T < 35 K. We have observed giant transverse magnetostriction (of the order of 10 −4 at 4.2 K) for magnetic field B c and longitudinal magnetostriction (of the order of 10 −5 at 4.2 K) for B ⊥ c orientation. Pronounced jumps in transverse magnetostriction have been observed in the temperature range between 4.2 K and 8.5 K. Experimental magnetostriction results are compared with magnetization measurements using a vibrating sample magnetometer and gradientometric Hall sensors measurements. The calculations were performed on the basis of a pinning-induced mechanism of magnetostriction. The simple adiabatic theory seems to be insufficient to describe the observed flux instabilities.

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