At room temperature a large magnetoresistance, IsR/R(H =0), of 60% has been observed in thin magnetic films of perovskitelike La-Ba-Mn-o, The films were grown epitaxially on SrTi03 substrates by oA'-axis laser deposition. In the as-deposited state, the Curie temperature and the saturation magnetization were considerably lower compared to bulk samples, but were increased by a subsequent heat treatment. The samples show a drop in the resistivity at the magnetic transition, and the existence of magnetic polarons seems to dominate the electric transport in this region. PACS numbers: 75.70.Ak, 72. 15.Gd, 73.50.Jt Giant magnetoresistance (GMR) due to spin-dependent scattering at the interface between ferromagnetic and nonmagnetic regions has been the subject of intense research in the last years [1-4]. At room temperature, resistance changes hR/R(H=0) as high as 40% have been observed in Cu/Co multilayers [2] and up to 11% in heterogeneous Cu/Co alloys [3,4], compared to only 2%-3% for "conventional" materials such as permalloy. A much higher magnetoresistance was found near a metal/insulator and simultaneous magnetic phase transition, e.g. , in Eu~-"Gd"Se [5], but in this material the eAect is restricted to temperatures below 50 K. The anomalous transport phenomena in these Eu-chalcogenide alloys have been explained by the appearance of giant spin molecules [6] and spin polarons [7]. Similar observations have been made in the mixed valence perovskitelike Ndo 5Pbo 5Mno3 in the region around the ferromagnetic phase transition at 184 K [8]. A large drop in resistivity and a high magnetoresistance AR/ R (0) & 50% was found, which is also believed to be caused by the existence of magnetic polarons. La2/3-Ba~g3Mno3 is also well known as a mixed valence metallic ferromagnet, but with a considerably higher Curie temperature of Tc =343 K [9,10]. At the Curie temperature a cusp in the resistivity was found and therefore gives rise to the assumption of a high magnetoresistance eAect at room temperature. Targets of stoichiometric composition were prepared by standard ceramic techniques from the metallic oxides and carbonates of 99.9% purity by repeated grinding and annealing in air. The x-ray diAraction patterns showed no other reAections than those of the rhombohedral unit cell found in Ref. [10] (a =0.3910 nm, y=90. 12'). Thin films of 150~10 nm thickness were grown on SrTi03 10&&10 mm substrates in (100) and (110) orientation. A laser deposition technique in off'-axis geometry was used, which had previously turned out to be a powerful tool in preparing high-T, superconducting thin films with a smooth surface [11]. Different substrate temperatures between 600 and 900 C were used, at a deposition pressure of 0.4 mbar oxygen. Epitaxial films were obtained for a substrate temperature of Tg =600 C as confirmed 250 T= 300K 200 8 A 0 bP c5 150 100 50 0:-0.0~a nnealed O 0.5 1.0 1.5 magnetic field p, H [T] 2.0 FIG. 1. Room temperature magnetization curve for the asdeposited sample (Ts =600'C) showing paramagnetic behav-ior. The ferroma...

To ensure future worldwide mobility, hydrogen storage in combination with fuel cells for on-board automotive applications is one of the most challenging issues. Potential solid-state solutions have to fulfil operating requirements defined by the fuel cell propulsion system. Important requirements are also defined by customer demands such as cost, overall fuel capacity, refuelling time and efficiency. It seems that currently none of the different storage solid state materials can reach the required storage densities for a hydrogen-powered vehicle. New strategies for storage systems are necessary to fulfil the requirements for a broad introduction of automotive fuel cell powertrains to the market. The combination of different storage systems may provide a possible solution to store sufficiently high amounts of hydrogen.

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The energy storage system is of decisive importance for all types of electric vehicles, in contrast to the case of vehicles powered by a conventional fossil fuel or bio-fuel based internal combustion engine. Two major alternatives exist and need to be discussed: on the one hand, there is the possibility of electrical energy storage using batteries, whilst on the other hand there is the storage of energy in chemical form as hydrogen and the application of a fuel cell as energy converter. The advantages and limitations, and also the impact of both options are described. To do so, existing GM concept vehicles and mass production vehicles are presented. Eventually, an outlook is given that addresses cost targets and infrastructure opportunities as well as requirements.