Magnetic Entropic Forces Emerging in the System of Elementary Magnets Exposed to the Magnetic Field.

A temperature dependent entropic force acting between the straight direct current I and the linear system (string with length of L ) of N elementary non-interacting magnets/spins μ→ is reported. The system of elementary magnets is supposed to be in the thermal equilibrium with the infinite thermal bath T . The entropic force at large distance from the current scales as Fmagnen~1r3, where r is the distance between the edge of the string and the current I , and kB is the Boltzmann constant; (r≫L is adopted). The entropic magnetic force is the repulsion force. The entropic magnetic force scales as Fmagnen~1T, which is unusual for entropic forces. The effect of "entropic pressure" is predicted for the situation when the source of the magnetic field is embedded into the continuous media, comprising elementary magnets/spins. Interrelation between bulk and entropy magnetic forces is analyzed. Entropy forces acting on the 1D string of elementary magnets that exposed the magnetic field produced by the magnetic dipole are addressed.