It is experimentally observed that irradiation of single crystal hematite Fe,O, leads to a decrease of the Morin spin-reorientation transition temperature and to the appearance of a reverse transition, i.e. to recovery of a weakly ferromagnetic phase at very low temperatures. Parameters of the new transition depend on the type and energy of particles. The possible reasons for the new transition and the formation mechanism of the disordered zones produced by atom-atom collision cascades are discussed. The splitting of the Mossbauer spectra in the temperature interval of the new transition undoubtedly shows that it is a first-order transition. 3KCnepHMeHTanbHO 06HapyXeH0, YTO 06~1yYeHWe MOHOKpUCTannOB reMaTATa Fe,O, IIpWBOnAT K CHIIXCHWIO TeMnepaTypbI CnWH-nepeOpIleHTarrIloHHoro nepeXOna Mopma W B03HWKHOBeHAIO 06-PaTHOrO nepCXOna, T. e. BOCCTdHOBJIeHAIO CJId60@eppOMarHHTHOfi @a361 IIpH OYeHb HW3KWX TeMnepa-TypaX. napaMeTpb1 HOBOrO IIepeXOna 3aBWCIlT OT TWna W 3HeprWA YaCTWU. 06cywnam~cs BO3MOXHbIe nPW4WHbl BOSHAKHOBeHUX HOBOrO IICpeXOAa, MeXaHIl3M B03HWKHOBeHIIR 3 0 H pa3ynOPIlAOYeHUIl, COSfiaHHbIX K a C K a n O M aTOM-ZTOMHbIX CTOJIKHOBeHA€%. PaCWenJIeHAe MeCC6ay3pOBCKIIX CneKTpOB B o 6 n a c~~ HOBOrO IIepeXOnd OAHOJHBYHO IIOKa3bIBaCT, YTO OH IlBJIReTCIl IIepeXOflOM I POW.') 480082 Alma-Ata, Republic of Kazakhstan.

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The magnetic properties of irradiated single crystal hematite are recovered by annealing. With increasing annealing temperature the amount of the weak ferromagnetic (WF) phase decreases at measurement temperature of 140 K, then the new low‐temperature transition temperature decreases while the Morin temperature increases. The annealing at 163 to 178 °C leads to the disappearance of the WF phase at low temperatures. The Morin transition temperature reaches its nonirradiated value only after annealing at 455 °C. In the single crystal hematite irradiated with 29 MeV α‐particles two stages of annealing are observed.

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