U.S. Philips Corporation

Leonardus A Van Hoof

Doeko Stoppels

Jan Haisma

Ulrich E Enz

Dieter W Mateika

Johannes A Pistorius

Horst Laudan

Peter G Boonen

A description is given of the composition and preparation of single phase crystals having a garnet structure and a lattice constant smaller than 11.9 .ANG.. The garnets correspond to the formula

Monocrystalline material having garnet structure

A magnetic head for a magnetic recording and playback device. The head comprises a Mn-Zn-ferrous ferrite core having a very high saturation magnetization and magnetic permeability. The Mn-Zn-ferrous-ferrite has a composition according to the formula

Magnetic head having a core of Mn-Zn-Co ferrous ferrite

The invention relates to a method of manufacturing bismuth germanate (Bi.sub.4 Ge.sub.3 O.sub.12) crystals using the Bridgman technique. A high degree of crystal perfection and an acceptable level of inclusions are obtained by changing the stoichiometry of the starting mixture in favor of Bi.sub.2 O.sub.3, such that the starting mixture contains between 40.2 and 40.5 mol. % of Bi.sub.2 O.sub.3 and between 59.8 and 59.5 mol. % of GeO.sub.2.

Method of manufacturing bismuth germanate crystals

A magnetic head for a magnetic recording and playback device includes a core having two core parts which are spaced from each other and between which a transducing gap is formed. The core consists of a (preferably monocrystalline) zinc-ferrous ferrite. A preferred range of compositions is defined by the formula

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Eindhoven, Netherlands

Leonardus A Van Hoof