The correct expression in accordance with Gauss’s law for magnetism is

Gauss law for magnetism states that total magnetic flux through a closed surface S will be zero. It is one of the four maxwell's equations that is useful in understanding the prinicples of electromagnetism. When understood in depth, the law implies that magnetic field lines form closed loops since they are continous. In short, it confirms that magnetic monopoles cannot exist.

F=-dU/dr in equilibrium position F = 0 and U is minimum

B-H curve drawn for only ferromagnetic material.