  The Mn-matrix was defined by Mohan [20] in which he has shown a method of
constructing (1,-1)-matrices and studied some of their properties. The
(1,-1)-matrices were constructed and studied by Cohn [5],Wang [33], Ehrlich [8]
and Ehrlich and Zeller[9]. But in this paper, while giving some resemblances of
this matrix with Hadamard matrix, and by naming it as M-matrix, we show how to
construct partially balanced incomplete block (PBIB) designs and some regular
bipartite graphs by it. We have considered two types of these M- matrices. Also
we will make a mention of certain applications of these M-matrices in signal
and communication processing, and network systems and end with some open
problems.
