The  paper of  the  month,  chosen  by  the Editor-in-Chief,  is  "Unusual Strain Resulted from InteractionBetween Permanent Magnets"  by V.I. Nizhankovskiy;

DOI: 10.12693/APhysPolA.145.57

Everybody is familiar with permanent magnets. Small, very strong permanent magnets are used in many devices, from toys to advanced electronic systems. This paper studies basic physical processes taking place in such magnets.

When a magnet is placed in a magnetic field, e.g. in the vicinity of another magnet, magnetic forces lead to stress forces and hence to deformation of the magnet. These deformations were studied in this paper. Experiments were done with cylindrical NdFeB magnets. Magnetostriction and elastic parameters of the magnet, namely the Young modulus and the Poisson ratio, were measured. Also the magnetic field distribution around the magnet was determined. The results of these investigations were used to predict the strain of the NdFeB magnet as a function of the magnetic field. All these experiments were nicely interpreted in the framework of the theory of elasticity. Thus a complete picture of processes taking place in permanent magnets is given.

Everybody who wants to learn what is going on when two strong magnets are placed close to each other should read this paper.

The Editor-in-Chief