Patent ID: 7455712

Claim:
Alloy particles of an alloy having a face-centered cubic structure, comprising: T and M in such a composition ratio that, when T is one or two selected from Fe and Co, and M is one or two selected from Pt and Pd, X in formula T x M 1-x is within the range of 0.3 to 0.7, and, with respect to (T+M), no more than 30 atomic percent (including zero percent) of metallic elements other than T and M, with the remainder being unavoidable impurities, the alloy particles having a TEM-measured average grain size (D TEM ) of not more than 50 nm, and a single crystallinity (D TEM )/(D x ) that is less than 1.50, where (D x ) is X-ray crystallite size, in which 90 or more out of 100 particles satisfy the equation (1) below and equation (2) below is satisfied, 0.90X av ≦X 1 , X 2 , . . . X 100 ≦1.10X av (1) Standard deviation σ of X 1 , X 2 , . . . X 100 ≦20% (2) provided that with respect to the value of X in the formula T x M 1-x , X av represents a measured particle value (value of X in the mean constituent of a particle assemblage), and of X 1 , X 2 , . . . X 100 represents the measured X value of each of 100 particles arbitrarily selected when the measurement field of view contains 1000 or more particles.