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US 6,599,234 B1Granted
Heating of magnetic material by hysteresis effects
AssigneeSirtex Medical Limited
InventorsBruce Nathaniel Gray, Raffaele Cammarano, Stephen Keith Jones
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AssigneeSirtex Medical Limited
InventorsBruce Nathaniel Gray, Raffaele Cammarano, Stephen Keith Jones
Estimating the term…
A magnetic material having a magnetic heating efficiency of at least 4.5×10−8 J.m/A.g in a cyclic magnetic field where the product of the amplitude and frequency of the applied field is less than or equal to 5×108 A/m.s, and the frequency of the applied filed is at least 20 kHz. The ideal magnetic material is characterized by a perfectly rectangular hysteresis loop, i.e. loop squareness of 1, with coercivity of 25 kA/m or less and high saturation magnetization. Preferably the magnetic material has a predominately cubic magnetic crystalline anisotropy. Preferably the magnetic material is a substituted magnetite (Fe3O4) or γ-ferric oxide (γFe2O3) crystalline lattice in which some of the iron atoms in that crystalline lattice have been substituted for one or more alternate metals atoms. Desirably, the metal atom is a member of the group: cobalt, zinc, nickel, manganese, magnesium, copper, chromium, gallium, cadmium.
A magnetic material having a magnetic heating efficiency of at least 4.5×10−8 J.m/A.g in a cyclic magnetic field where the product of the amplitude and frequency of the applied field is less than or equal to 5×108 A/m.s, and the frequency of the applied field is at least 20 kHz and wherein (i) the magnetic material is a substituted magnetite (Fe3O4) or gamma ferric oxide (γ-Fe2O3) crystalline lattice in which some of the iron atoms in that crystalline lattice have been substituted for one or more alternate metal atoms and (ii) the magnetic material has a predominantly cubic magnetocrystalline anisotropy.
An antipilferage device comprising a magnetic material having a magnetic heating efficiency of at least 4.5×10−8 J.m/A.g in a cyclic magnetic field where the product of the amplitude and frequency of the applied field is less than or equal to 5×108 a/m.s, and the frequency of the applied filed is at least 20 kHz and wherein (i) the magnetic material is a substitute magnetite (Fe3O4) or gamma ferric oxide (γFe2O3) crystalline lattice in which some of the iron atoms in that crystalline lattice have been substituted for one or more alternate metals atoms and (ii) the magnetic material has a predominately cubic magnetocrystalline anisotropy.
Dependencies are inferred from the claim text.