Magnetorheological fluid and device

A magnetorheological fluid comprising:

• magnetic particles;
• resin particles;
• and
• a dispersion medium, wherein
• a proportion constituted by mass of the magnetic particles relative to total mass of the magnetorheological fluid is 35 mass % to 95 mass %,
• a proportion constituted by mass of the resin particles relative to total mass of the magnetorheological fluid is 0.3 mass % to 20 mass %,
• the resin particles have an average particle diameter of 20 nm to 1,500 nm,
• the dispersion medium includes a compound including at least two types of groups that interact with the magnetic particles in one molecule,
• a proportion constituted by mass of the compound relative to total mass of the dispersion medium is 50 mass % or more, and
• a proportion constituted by mass of the dispersion medium relative to total mass of the magnetic particles, the resin particles, and the dispersion medium is 5 mass % to 45 mass %.