Thermo-magnetic recording head

Claim 2

A magnetic head comprising: a gap of a first material with magnetic properties at ambient temperature; heating means to heat the material of the gap beyond the Curie temperature in order to make said gap material lose its magnetic properties; and magnetic pole pieces of a second material on each side of the gap said pieces forming electrical conductors for conveying heating current to heat the gap material.

Claim 3

A magnetic head according to claim 1, wherein the Curie temperature of the second material of the pole pieces is greater than the Curie temperature of the gap material.

Claim 4

A magnetic head according to claim 1 or 2, wherein the resistivity of the material of the gap is greater than the resistivity of the second material of the pole pieces.

Claim 5

A magnetic head according to claim 3, wherein the ratio between the resistivity of the material of the gap and the resistivity of the material of the pole pieces is greater than 10,000.

Claim 6

A magnetic head according to any one of the claims 1, 2 or 3, wherein the resistivity of the pole pieces ranges between 10 and 100 μΩcm.

Claim 7

A magnetic head according to any one of the claims 1, 2, or 3, wherein the resistivity of the material of the gap is 10 Ωcm at the most.

Claim 8

A magnetic head according to claim 6, wherein the resistivity of the material of the gap is greater than 0.1 Ωcm.

Claim 9

A magnetic head according to claim 1, wherein the material forming the pole pieces is chosen from the following groups: iron and nickel alloy, iron, silicon and aluminium alloy, cobalt and zirconium alloy, and pure iron.

Claim 10

A magnetic head according to claim 1, wherein the material forming the gap is an iron oxide.

Claim 11

A magnetic head according to claim 9, wherein the material forming the gap is a ferrite of manganese, zinc and lithium.

Claim 12

A magnetic head according to any one of the claims 1, 2 or 3, wherein the Curie temperature of the material of this gap ranges between 60° and 150° C.

Claim 13

A magnetic head according to any one of the claims 1, 2 or 3, wherein the pole pieces and the gap are deposited in thin layers on a substrate.

Claim 14

A magnetic head according to claim 12, wherein each pole piece ia associated with a conductive metallic layer.

Claim 15

A magnetic head according to claim 13, wherein the metallic layers are interposed between the layers of pole pieces and the substrate.

Claim 16

A magnetic head according to claim 12, wherein an electrically insulating and thermally insulating layer is interposed between the substrate and the layers of pole pieces and of the gap.

Claim 17

A magnetic head according to claim 12, wherein the gap layer forms the shoulder of a layer with a thickness smaller than an adjacent pole piece layer, and on which there is deposited the second pole piece.

Claim 18

A magnetic head according to any one of the claims 1, 2 or 3, wherein the material forming the gap has a resistivity which gets lower when the temperature increases so as to show a characteristic of negative resistance (NTC).

Claim 19

A magnetic head according to claim 17, wherein the gap material is an iron oxide, notably a ferrite of manganes, zinc and lithium.

Claim 20

A magnetic head according to claim 1, wherein the Curie temperature of the pole pieces ranges between 200° C. and 400° C.

Claim 21

A magnetic head having two pole pieces of thin layers of first and second thicknesses wherein said pole pieces are separated by gap of a first material, wherein the gap material is extended to form a shoulder layer on which there is deposited one of said two pole piece thin layers having a first thickness, said gap shoulder layer having a thickness less than the thickness of the other one of said pole piece layers having said second thickness and wherein said gap material is a material which is magnetic at ambient temperature, said magnetic head further including a heating means for heating the gap material to a temperature above the Curie point in order to make said gap material lose its magnetic properties.

Claim 22

A magnetic head having two pole pieces of thin layers of first and second thicknesses wherein said pole pieces are separated by gap of a first material, wherein the gap material is extended to form a shoulder layer on which there is deposited one of said two pole piece thin layers having a first thickness, said gap shoulder layer having a thickness less than the thickness of the other one of said pole piece layers having said second thickness and wherein said gap material is a material which is magnetic at ambient temperature, said magnetic head further including a heating means for heating the gap material to a temperature above the Curie point in order to make said gap material lose its magnetic properties.

Claim 25

A device according to claim 22, wherein the second pole pieces of the heads are in the form of parallel strips of the same width, the strips located on one and the same side of the common pole piece being separated by an interval with a width equal to the width of each strip.