R-t-b based sintered magnet and rotating machine

An R-T-B based sintered magnet comprising

• R2T14B crystal grains, and a grain boundary formed between or among two or more adjacent R2T14B crystal grains,
• Ga in an amount in a range of from 0.1 mass % to 1.0 mass %,
• Co in an amount in a range of from 0.3 mass % to 3.0 mass %,
• Cu in an amount in a range of from 0.05 mass % to 1.5 mass %,
• N, and
• Zr in an amount in a range of from 0.01 mass % to 1.5 mass %, wherein
• R represents at least one rare earth element and a content of R in the R-T-B based sintered magnet is in a range of from 29.5 mass % to 33 mass %,
• T represents one or more transition metal elements comprising Fe or a combination of Fe and Co,
• a content of B in the R-T-B based sintered magnet is in a range of from 0.75mass % to 0.95 mass %,
• the grain boundary contains R—Ga—Co—Cu—N concentrated parts, each of which is a single, continuous area within the grain boundary in which concentrations of R, Ga, Co, Cu, and N are higher than those in the R2T14B crystal grains respectively,
• the R—Ga—Co—Cu—N concentrated parts are separate from an R-—rich phase in the grain boundary,
• a number of Ga atoms in the R—Ga—Co—Cu—N concentrated part is in a range of from 7 to 16% of a total atom number of R, Fe, Ga, Co, Cu, and N,
• a number of Co atoms in the R—Ga—Co—Cu—N concentrated part is in a range of from 1 to 9% of a total atom number of R, Fe, Ga, Co, Cu, and N,
• a number of Cu atoms in the R—Ga—Co—Cu—N concentrated part is in a range of from 4 to 8% of a total atom number of R, Fe, Ga, Co, Cu, and N, and
• a number of N atoms in the R—Ga—Co—Cu—N concentrated part is in a range of from 1 to 13% of a total atom number of R, Fe, Ga, Co, Cu, and N.