Method for producing sputtering target material

A method of producing a sputtering target material composed of an alloy M comprising B, and Co and/or Fe, with a balance consisting of inevitable impurities, the method comprising a sintering step of sintering a mixed powder obtained by mixing a first powder and a second powder,

• wherein the first powder and the second powder each consist of particles,
• wherein each particle forming the first powder is composed of an alloy M1 comprising B, and Co and/or Fe, with a balance consisting of inevitable impurities,
• wherein a proportion of a B content to a total of a Co content, an Fe content, and a B content in the alloy M1 is from 40 at. % to 60 at. %,
• wherein each particle forming the second powder is composed of an alloy M2 comprising B, and Co and/or Fe, with a balance consisting of inevitable impurities,
• wherein a proportion of a B content to a total of a Co content, an Fe content, and a B content in the alloy M2 is from 20 at. % to 35 at. %,
• wherein a proportion of a B content to a total of a Co content, an Fe content, and a B content in the mixed powder is from 33 at. % to 50 at. %,
• wherein a metallographic structure comprising a (CoFe)2B phase in which an atomic ratio of a sum of a Co content and an Fe content (Co content+Fe content) to a B content [(Co content+Fe content):B content] is 2:1, and a (CoFe) B phase in which the atomic ratio [(Co content+Fe content):B content] is 1:1 is formed in the sintering step, and
• wherein a boundary length per unit area Y (1/μm), which is obtained by measuring a boundary length between the (CoFe)2B phase and the (CoFe) B phase using a scanning electron microscope, and a proportion X (at. %) of a B content to a total of a Co content, an Fe content, and a B content in the alloy M satisfy the following expression:
• Y<−0.0015×(X−42.5)2+0.15.