Manifestation of ferromagnetism in lightly oxygen-doped La2CuO4 single crystals in magnetic fields H<50 Oe

The temperature and field dependences χ(T,H) in La₂CuO_4+δ single crystals with δ<0.015 have been investigated in magnetic fields 0.1<H<450 Oe by the differential magnetic susceptibility method. It was found that under oxygen doping conditions ferromagnetic regions are formed. These regions produce a characteristic curve of the magnetic susceptibility χ(T,H), which is observed only in magnetic fields of less than 50 Oe. This can be explained by the formation of ferrons [A. Aharony et al. Phys. Rev. Lett. 60, 1330 (1988); L. I. Glazman and A. S. Ioselevich, Z. Phys. B 80, 268 (1990)] in an antiferromagnetic matrix. Pis’ma Zh. éksp. Teor. Fiz. 64, No. 3, 152–155 (10 August 1996)