The magnet remains stable,if it align itself with the field as its potential will be minimum in that position.\\\\(\\mu=-\\vec{M}.\\vec{B}\\\\)=\\\\(-MB\\cos \\Theta \\\\)The potential energy will be minimum if \\\\(\\Theta =0\\\\)i.e. \\\\(-MB\\\\)\\\\(\ herefore \\\\) If it is parallel to magnet field