Abstract: A magnetic recording medium is described, comprising a nonmagnetic support having thereon a magnetic layer containing a binder which is cross-linkable or polymerizable by radiation irradiation and ferromagnetic particles, the ferromagnetic particles being metal or metal alloy particles mainly comprising iron having a crystal size of 300 .ANG. or less, having an atomic ratio of oxygen atoms to iron atoms of from 1.6 to 3.0 on the surface of the particles, and the magnetic layer having been irradiated with radiation, and comprising a nonmagnetic support having thereon a magnetic layer containing a binder comprising thermoplastic resins, thermosetting resins, reactive type resins and mixtures thereof and ferromagnetic particles, said ferromagnetic particles being metal or metal alloy particles mainly comprising iron having a crystal size of 250 .ANG. or less, and having an atomic ratio of oxygen atoms to iron atoms of from 1.6 to 3.0 on the surface of said particles.

Abstract: A magnetic recording medium comprising a nonmagnetic support and a magnetic recording layer provided on the support, wherein the magnetic recording layer contains a compound having a polar group (i.e., a carboxylic acid group, a carboxylic acid salt group, a sulfonic acid group or a sulfonic acid salt group) which is bonded to an aromatic ring directly or indirectly through a polymethylene group having not more than 4 carbon atoms or an unsaturated straight-chain hydrocarbon group having not more than 4 carbon atoms.

Abstract: Vincaminic acid derivatives represented by the formula ##STR1## wherein R.sup.1 is a hydrogen atom, an alkyl group having 1 to 8 carbon atoms or an alkoxyalkyl group having 2 to 6 carbon atoms, R.sup.2 is a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, a halogenated alkyl group having 1 to 5 carbon atoms, a cycloalkyl group having 3 to 6 carbon atoms, an alkoxycarbonylallyl group having 3 to 8 carbon atoms, an alkenyl group having 2 to 4 carbon atoms, a phenyl group, a phenyl group substituted by alkoxy groups each having 1 or 2 carbon atoms or a thienyl group, A is a hydroxy group, B is a hydrogen atom, or A and B together form a valence bond, and the acid addition salts thereof are disclosed. These compound are useful as thereapeutic effect on cerebovascular injuries.

Abstract: A magnetic recording medium comprising a non-magnetic support having provided thereon plural magnetic layers containing ferromagnetic particles and binders, wherein the ferromagnetic particles contained in the uppermost magnetic layer have an average long axis length measured by a transmission electron microscope of 0.25 .mu.m or less and a crystal size measured by an X-ray deffractiometory of 300 .ANG. or less, and the ferromagnetic particles contained in the magnetic layers other than the uppermost layer have an average long axis length measured by a transmission electron microscope of 0.25 .mu.m or less and a crystal size measured by an X-ray deffractiometory of 250 .ANG. more, provided that the ferromagnetic particles of the uppermost layer have a crystal size measured by an X-ray deffractiometory smaller than the crystal size measured by an X-ray deffractiometory of the ferromagnetic particles of the magnetic layers other than the uppermost layer.

Abstract: An improvement of a magnetic recording medium comprising a nonmagnetic support and a magnetic recording layer provided on the support which comprises a binder and a ferromagnetic powder dispersed therein is disclosed. The binder contains a resin component having a metal sulfonate group and the ferromagnetic powder contains water in an amount corresponding to moles of 20-80 times as much as the number of moles of the metal sulfonate group contained in the binder.

Abstract: An improvement of a magnetic recording medium comprising a nonmagnetic support and a magnetic recording layer provided on the support which comprises a binder and a ferromagnetic powder dispersed therein is disclosed. The binder contains a resin component having an epoxy group and the ferromagnetic powder contains water in an amount corresponding to moles of 1-5 times as much as the number of moles of the epoxy group contained in the binder.

Abstract: A magnetic recording medium contains in its magnetic recording layer a ferromagnetic metal powder containing an aluminum component in an amount of 1 to 6% by weight as alumnum metal, and an extremely hard abrasive such as .alpha.-alumina, chrome oxide, silicon carbide and silicon nitride. A magnetic recording medium preferably contains in its magnetic recording layer a binder comprising a resin component having a polar group.

Abstract: A magnetic recording medium is described, having improved carrier noise ratio and weather resistance, by controlling the content and the crystal size of iron nitride which contains iron oxide or .epsilon.-Fe.sub.x N (2<x.ltoreq.3).

Abstract: A process for producing a ferromagnetic metal powder comprising treating acicular iron oxyhydroxide or an acicular metal oxyhydroxide composed mainly of iron with a silicon compound, dehydrating the treated material by heating the material in a non-reducing atmosphere to produce iron oxide particles or metal oxide particles composed mainly of iron, and reducing the resulting iron oxide particles or metal oxide particles composed mainly of iron by heating in a reducing atmosphere to produce iron powder or a metal powder composed mainly of iron, which is characterized in that the dehydration by heating in a non-reducing atmosphere is carried out at a temperature of from 300.degree. to 800.degree. C. and the iron oxide particles or the metal oxide particles composed mainly of iron are treated with a silicon compound prior to reduction by the heating in a reducing atmosphere.