Colossal magnetocapacitance and scale-invariant dielectric response in phase-separated manganites

Thin films of strongly-correlated electron materials (SCEM) are often grown epitaxially on planar substrates and typically have anisotropic properties that are usually not captured by edge-mounted four-terminal electrical measurements, which are primarily sensitive to in-plane conduction paths. Accordingly, the correlated interactions in the out-of-plane (perpendicular) direction cannot be measured but only inferred. We address this shortcoming and show here an experimental technique in which the SCEM under study, in our case a 600 Angstrom-thick (La1-yPry)0.67Ca0.33MnO3 (LPCMO) film, serves as the base electrode in a metal-insulator-metal (MIM) trilayer capacitor structure. This unconventional arrangement allows for simultaneous determination of colossal magnetoresistance (CMR) associated with dc transport parallel to the film substrate and colossal magnetocapacitance (CMC) associated with ac transport in the perpendicular direction. We distinguish two distinct strain-related direction-dependent insulator-metal (IM) transitions and use Cole-Cole plots to establish a heretofore unobserved collapse of the dielectric response onto a universal scale-invariant power-law dependence over a large range of frequency, temperature and magnetic field.Comment: 32 pages, 4 figures, Supplementary section included, Submitted to Nature Physic

Sliding charge density wave in manganites

The so-called stripe phase of the manganites is an important example of the complex behaviour of metal oxides, and has long been interpreted as the localisation of charge at atomic sites. Here, we demonstrate via resistance measurements on La_{0.50}Ca_{0.50}MnO_3 that this state is in fact a prototypical charge density wave (CDW) which undergoes collective transport. Dramatic resistance hysteresis effects and broadband noise properties are observed, both of which are typical of sliding CDW systems. Moreover, the high levels of disorder typical of manganites result in behaviour similar to that of well-known disordered CDW materials. Our discovery that the manganite superstructure is a CDW shows that unusual transport and structural properties do not require exotic physics, but can emerge when a well-understood phase (the CDW) coexists with disorder.Comment: 13 pages; 4 figure

Long range electronic phase separation in CaFe3O5

Electronic phase separation is an important feature of many correlated perovskite compounds but hasn’t been seen in other complex oxides with similar physical behaviour such as magnetite. Hong et al. find phase separation between a magnetite-like charge ordered phase and a charge averaged phase in CaFe3O5

Between the hammer of globalization and the anvil of nationalism: is Europe's complex diversity under threat?

Cultural diversity is very often conceived in relationship with the nation-state, but rarely problematized in tandem with transnational forces like political and economic globalization. The article begins by recognizing the need, and the difficulty, of studying both these forces simultaneously in relation to cultural diversity. As a supranational set of institutions, the European Union provides an ideal framework in which to assess the simultaneous impact of the nation-state and globalization on cultural diversity. The EU unification project, based on a pluralist, multicultural and multilateral vision of Europe, is diametrically opposed to previous state-making practices centred on rigid notions of internal uniformity and gravitating around the practices of ‘nation-statism’. This article first proposes the notion of ‘cultural homogenization’ as an explanatory tool to identify the role of normative visions of culture associated with the nationalizing practices of most modern nation-states. It then connects this to the scholarly literature on ‘nation-building’ and focuses particularly on its critique within theories of nationalism. This in turn is associated with various resurrected pluralist arrangements which have emerged in Europe, like cultural autonomy, multiculturalism and particularly, ‘consociationalism’. However, the article identifies a more immediate challenge to cultural diversity in the de-regulative policies associated with neo-liberal globalization. It concludes that, although European consociationalism remains a well-established and time-honoured tool for stabilizing inter-cultural relations and maintaining pluralist coexistence, it does not, and cannot, provide an incentive and framework for accommodating the normative and cultural conflicts unleashed by neo-liberal globalization