1. An information recording medium, comprising a recording layer whose phase changes by irradiation with a laser beam or application of current, wherein the recording layer contains, as its main component, a composite composed of Ge and Sb that are essential components, and Te that is an optional component, and the composite has a composition within a region enclosed by: point (a) (35, 65, 0), point (b) (36.9, 60, 3.1), point (c) (3.2, 60, 36.8), and point (d) (5, 95, 0) in terms of a coordinate (Ge, Sb, Te)=(x, y, z) on a triangular coordinate shown in FIG. 1 , where point (b) corresponds to a point at Sb=60 on Ge 60 Te 40 —Ge 35 Sb 65 , point (c) corresponds to a point at Sb=60 on Te—Ge 5 Sb 95 and the region includes lines extending between point (a) and point (b), point (b) and point (c), point (c) and point (d), and point (d) and point (a).