Elastic properties of ferromagnetic EuB6

Results of ail ultrasonic investigation of EuB6 at low temperatures are rep orted. Both longitudinal and transverse acoustic modes exhibit anomalies in the vicinity of the low-temperature phase transition,) of EuB6. The ultras ound data serve to establish part of the B-T phase diagram of EuB6. At magn etic fields exceeding 3 T, magneto-acoustic quantum oscillations (MAQO) are observed. The nature of the acoustic anomalies and possible phases in exte rnal magnetic fields are discussed. Also a comparison with the elastic prop erties of other rare-earth (RE) hexaboride compounds is made.