Remarks on the sharp partial order and the ordering of squares of matrices

In this note we revisit the sharp partial order introduced by Mitra [S.K. Mitra, On group inverses and the sharp order, Linear Algebra Appl. 92 (1987) 17-37]. We recall some already known facts from certain matrix decompositions and derive new statements, relating our discussion to recent results in the literature concerned with partial orders between matrices and their squares.