The current spin on manganites

Abstract

STANDFIRST:Manganites are pseudo-cubic oxides of manganese that show extremes of functional behavior. Diverse magnetic and electronic phases coexist on a wide range of length scales even within single crystals. This coexistence demonstrates a complexity that inspires ever deeper study. Yet even the basic nature of the coexisting phases remains controversial. Can the ferromagnetic metallic phase provide fully spin-polarized electrons for spin electronics? Does the superlattice in the highly insulating phase represent charge order? Here we highlight recent results that demonstrate a coexistence of opinions about a field in rude health. ABSTRACT:In a material, the existence and coexistence of phases with very different magnetic and electronic properties is both unusual and surprising. Manganites in particular capture the imagination because they demonstrate a complexity that belies their chemically single-phase nature. This complexity arises because the magnetic, electronic and crystal structures interact with one another to deliver exotic magnetic and electronic phases that coexist. This coexistence is self-organized and yet readily susceptible to external perturbations, permitting subtle and imaginative experiments of the type that we describe here. Moreover, these experiments reveal that each competing phase itself remains an incompletely solved mystery.Manganites were known to show pronounced magnetoresistance 1,2 and phase separation 3 effects in the 1950s, but they really hit the heights during the 1990s for three reasons. First, magnetoresistance took prominence between the 1988 discovery 4 of giant magnetoresistance (GMR) in metallic multilayers, and the first shipment of GMR discdrive heads by IBM in 1998. Second, great advances in laboratory infrastructure permitted new approaches, e.g. the fabrication of high-quality thin films, the advent of superconducting magnets, and the imaging of magnetic and electronic texture via e.g. scanning probe techniques. Third, this infrastructure had been very productive in the study of the high-temperature cuprate superconductors, and scientists were therefore immediately able to accept the new challenges presented by the manganites.The manganites are a family of perovskite oxides in which the composition of the Asite cations may be varied using mixtures of divalent rare-earth and trivalent alkalineearth elements. The most immediate consequence of this variation is to alter the charge doping of the magnetic and electronic structures that reside in the sublattice formed by the B-site manganese and intervening oxygen atoms. Significantly charge disorder on the

Compact X-ray Light Source Workshop Report

“…For example, the electrical conductivity of perovskite manganites can be made exquisitely sensitive to external stimuli, such as temperature, pressure, and optical and magnetic fields (colossal magnetoresistance), by doping and applied strain (Ahn et al 2004;Kim et al 2010). This behavior, thought to be due to the coexistence of multiple phases and competition between the various degrees of freedom in these materials, is poorly understood at relevant length and time scales (Israel et al 2007;Shenoy and Rao 2008;Weber et al 2009). Despite a large body of experimental work on the average properties of these materials, a general understanding of the individual phases and mechanisms behind their coexistence remains largely unexplored.…”

Ageing effects on electrical resistivity and magnetoresistance of nanostructured manganite films

“…The resistivity (ρ) as a function of temperature (T) measured just after sample preparation, i. e. after deposition of the Ag electrodes and annealing them at 420 °C for 50 minutes, for the LSMOslow films is presented by the square symbols (1) in Fig. 1.…”

“…Doped perovskite manganites exhibiting colossal magnetoresistance (CMR) effects have attracted considerable attention not only for fundamental research, but also for potential device applications [1]. The investigations of such polycrystalline films and bulk materials have revealed several advantages in comparison with epitaxial films or single crystal manganites [2].…”

“…This technological process and annealing in a different gas atmosphere can change the electrical parameters of the active element (manganite film) of the device. Therefore, the ageing effects which influence the stability of the electrical resistivity of thin polycrystalline manganite films over time play an important role in the development of these devices [1].…”

Magnetization dynamics in La0.67Ca0.33MnO3 epitaxial films probed with resonant and non-resonant microwave absorption

“…5 During recent years, the phenomenon of magnetic phase separation near the Curie temperature (T C ) has attracted wide spread interest because of its potential application as memristor devices. 6 While several probes have been used to study phase separation in manganites, the coexisting of various ferromagnetic, paramagnetic and antiferromagnetic phases, their anisotropies and the dynamics of magnetization can be addressed in a rigorous manner using the electron spin resonance (EPR) technique. [7][8][9][10][11][12][13] For example, Tovstolytkin et al 7 have used EPR to investigate the complex phase separation in La 0.6 Ca 0.4 MnO 3 films grown on NdGdO 3 (001) under specific condition.…”