An ultrafine-crystalline alloy ribbon having a composition represented by the general formula of Fe.sub.100-x-y-zA.sub.xB.sub.yX.sub.z, wherein A is Cu and/or Au, X is at least one element selected from the group consisting of Si, S, C, P, Al, Ge, Ga and Be, and x, y and z are numbers meeting the conditions of 0<x5, 8y22, 0z10, and x+y+z25 by atomic %, and a structure in which ultrafine crystal grains having an average particle size of 30 nm or less being dispersed in a proportion of more than 0% and less than 30% by volume in an amorphous matrix; an ultrafine crystal grains-depleted region comprising ultrafine crystal grains at a number density of less than 500/m.sup.2 being formed in a region of 0.2 mm in width from each side of the ribbon.

A recording medium is provided, such as paper, secured by magnetic microwires. The recording medium comprises: a pulp structure formed by pulp fibers, said pulp structure carrying microwires having a metal core of a predetermined material composition, and an insulating layer coating on said metal core; and at least one coating layer on at least one side of said pulp structure. The pulp structure is a single-layer structure with the microwires fully embedded in said single layer, the microwires having cross-sectional dimensions approximately equal to cross-sectional dimensions of the pulp fibers.