Andreev reflection at a Pb/CrO(2) point contact has been used to determine the spin polarization of single-crystal CrO(2) films made by chemical vapor deposition. The spin polarization is found to be 0.96 +/- 0.01, which confirms that CrO(2) is a half-metallic ferromagnet, as theoretically predicted.

The low-field magnetoresistance (MR) properties of polycrystalline La0.67Sr0.33MnO3 and La0.67CaO33MnO3 thin films with different grain sizes have been investigated and compared with epitaxial films. MR as high as 15% has been observed in the polycrystalline films at a field of 1500 Oe at low temperatures, whereas the MR of the epitaxial films is less than 0.3% in the same field range. Based on the magnetization dependence of the MR, the current-voltage characteristics, and the temperature dependence of the resistivity, we attribute the low-field MR to spin-dependent scattering of polarized electrons at the grain boundaries which serve as pinning centers for the magnetic domain walls.

We have used a self-aligned lithographic process to fabricate magnetic tunnel junctions of La 0.67 Sr 0.33 MnO 3 down to a few micrometers in size. We have obtained a magnetoresistance ratio as large as 83% at low magnetic fields of a few tens of Oe, which correspond to the coercivities of the magnetic layers. Transmission-electron-microscopy analysis has revealed the heteroepitaxial growth of the trilayer junction structure, La 0.67 Sr 0.33 MnO 3 /SrTiO 3 /La 0.67 Sr 0.33 MnO 3 . We have observed current-voltage characteristics typical of electron tunneling across an insulating barrier. The large magnetoresistance is likely due to the nearly half-metallic electronic structure of the manganites.

We report on the fabrication of a new class of trilayer epitaxial thin film devices based on the doped perovskite manganates La–Ca–Mn–O and La–Sr–Mn–O. We show that large resistance changes, up to a factor of 2, can be induced by a moderate applied magnetic field below 200 Oe in these trilayers supporting current-perpendicular-to-plane transport. These results show that low-field spin-dependent transport in manganates can be accomplished, the magnitude of which is suitable for magnetoresistive field sensors.

Of the 605 patients seen since 1973, 336 patients have been treated with sodium valproate (VPA) alone or in combination with drugs other than carbamazepine (CBZ). Of these 336, 240 have been on monotherapy, of whom 200 are seizure-free. Follow up has been longer than 3 years in 78%. Complete control of seizures has been achieved in more than 80% of patients with absence, myoclonic, and primary tonic-clonic seizures, in 72% of those with photosensitive epilepsy including eyelid myoclonia, and in 47% of partial epilepsies, for which carbamazepine was the initial drug of choice. Only 21% of those with myoclonic astatic epilepsy have become free from seizures. At first VPA was given twice daily, but in recent years it was given once daily, as this was more effective. Reasons for failure of VPA therapy are given. Side effects in 436 patients (100 more patients were added for this assessment only) were uncommon, though where they did occur, weight increase was the most frequent. Platelets were reduced without clinical problems. There were no severe hepatic disorders. Serum levels were assessed in seizure-free patients, and the optimum level was between 60 and 120 mg/L (most patients received between 20 and 30 mg/kg). VPA was given during 30 pregnancies, and there was no evidence of teratogenicity on monotherapy. VPA is most effective in primary generalized epilepsy, especially if given as the sole antiepileptic drug. If the daily dose does not exceed 40 mg/kg or 2.5 g, it is singularly free from serious side effects.