Griffiths phase, metal-insulator transition, and magnetoresistance of doped manganites

Abstract

A phenomenological model is developed for systematic study of the universal features in metal-insulator transition and magnetoresistivity of mixed-phase manganites. The approach is based on utilization of some hypothesis appropriate to the Preisach picture of the magnetization process for half-metallic ferromagnets and an assumption that in doped manganites a Griffiths-type phase exists just above the magnetic-ordering temperature. Within the model, the system is considered as a random three-dimensional resistor network where a self-consistent formation of paths with metal and polaron types of conductivity is not only due to magnetic field variation but also due to temperature changes, as well. Both mechanisms of intrinsic percolation transition are considered on one basis. The theory is able to replicate the basic regularities found experimentally for doped manganites resistivity dependence on temperature and magnetic field without the need for empirical input from the magnetoresistive data. Within the approach a natural basis has arisen for a qualitative classification of magnetoresistive materials into those, such as La 0.7 Sr 0.3 MnO 3 , showing modest magnetoresistivity, and those, such as La 0.7 Ca 0.3 MnO 3 , showing large magnetoresistivity.

Possible realization of an antiferromagnetic Griffiths phase in Ba(Fe1−xMnx)2Inosov1, Friemel2, Park3 et al. 2013Phys. Rev. B485840View full textAdd to dashboardCite

“…In particular, quantum phase transitions can be smeared because of the coexistence of disordered (paramagnetic) regions and locally ordered clusters within the so-called Griffiths region of a phase diagram, 2,3,10 which has been observed experimentally in various real materials. [11][12][13][14][15][16][17][18] The specifics of itinerant magnetic systems, [19][20][21] which are of the most relevance to our present study, is determined by the presence of long-range Ruderman-Kittel-Kasuya-Yosida (RKKY) interactions [22][23][24][25] between local magnetic moments that induce correlations between the magnetically ordered rare regions, leading to the formation of so-called cluster glass (CG) phases preceding uniform ordering. [26][27][28][29] At present, theoretical understanding of rare-region effects in itinerant systems still remains a topic of active research and is yet far from being complete.…”

Formation of Nanosize Griffiths-like Clusters in Solid Solution of Ferromagnetic Manganite and Cobaltite

“…As a result, a FM metal to PM insulator transition occurs when the concentration of metallic bond reaches the percolation threshold at a temperature close to T C . Phenomenological models based on effective medium approach suggest that both MI transition and GP are due to the percolative nature of electrical conduction 8,15 . The situation is slightly different for La 1−x Sr x MnO 3 system.…”

Structure, magnetic, and magnetocaloric properties of amorphous and crystalline La0.4Ca0.6MnO3+δ nanoparticles

“…Fitting to the Curie-Weiss law shows an increase of the Curie temperature from 145 K to 250 K as particle size is increased from 25 nm to 130 nm. The downturn in −1 in the 130 nm and 50 nm samples is characteristic of the onset of a Griffiths-like phase, a well-known phenomenon in doped manganites [25][26][27][28]. Induced by disorder, the Griffiths phase features FM clusters within the PM phase between the Curie temperature of the undiluted system (T G ) and the actual magnetic ordering temperature (T C (p)).…”