arXiv subjects

E. L. Nagaev

Publications and source records attributed to E. L. Nagaev.

3 recordsLinked to original sources

arXiv2002

Large nonzero-moment magnetic strings in antiferromagnetic crystals of the manganite type

The magnetic strings in antiferromagnetic crystals with the spin $S = 1 /2$ differ from the magnetic polarons (ferrons) by the absence of the additional magnetic moment. We show that in the $S > 1 /2$ double exchange crystals with the antiferromagnetic $s-d$ exchange, a new type of magnetic strings appears, which possesses a magnetic moment. It is concentrated at the center of the string, and the magnetized string is, in its essence, the state intermediate between the string and the ferron. In antiferromagnetic manganites, this moment is by an order of magnitude larger than that of a magnetic atom. Unlike the conventional ferrons, the magnetization of the strings exists at any parameters of the crystals under consideration. We argue that this new type of magnetic state can be relevant to some doped antiferromagnets including manganites.

cond-mat.str-el↗

arXiv2002

Resistivity extrema in double exchange ferromagnetic nondegenerate semiconductors

A version of the magnetoimpurity theory of the colossal magnetoresistance materials suitable for the double exchange ferromagnetic nondegenerate semiconductors is presented. It provides an explanation of the nonmonotonic temperature dependence for the charge carrier density in them when it displays first a maximum and then a minimum, on increase in temperature. Respectively, the resistivity displays first a minimum and then a maximum. The theory is based on the relation between the charge carrier activation energy and the change in the magnon free energy caused by the ionization of an impurity. This is tantamount to the relation between the charge carrier density and the so called giant red shift of the optical absorption edge.

cond-mat.str-el↗

arXiv2000

The phase-separated states in antiferromagnetic semiconductors with polarizable lattice

The possibility of the slab or stripe phase separation (alternating ferromagnetic highly- conductive and insulating antiferromagnetic layers) is proved for isotropic degenerate antiferromagnetic semiconductors. This type of phase separation competes with the droplet phase separation (ferromagnetic droplets in the antiferromagnetic host or vice versa). The interaction of electrons with optical phonons alone cannot cause phase-separated state with alternating highly-conductive and insulating regions but it stabilizes the magnetic phase separation. The magnetostriction deformation of the lattice in the phase-separated state is investigated.

cond-mat.str-el↗