Magnetic core element for antenna, thin-film antenna, and card equipped with thin-film antenna

A magnetic core element in the form of an nano-crystalline alloy strip of a thickness of 25 .mu.m or less having a chemical composition represented by:

• (Fe.sub.1-v M.sub.v).sub.100-x-y-z-w A.sub.x M'.sub.y M".sub.z X.sub.w( 2)
• wherein M is Co, Ni or a combination thereof;
• A is Cu, Au or a combination thereof;
• M' is at least one element selected from the group consisting of Ti, V, Zr, Nb, Mo, Hf, Ta and W;
• M" is at least one element selected from the group consisting of Cr, Mn, Al, Sn, Zn, Ag, In, platinum group elements, Mg, Ca, Sr, Y, rare earth elements, N, O and S;
• X is at least one element selected from the group consisting of B, Si, C, Ge, Ga and P;
• v is a numerical value satisfying 0.ltoreq.v.ltoreq.0.5;
• and x, y, z and w are atomic percentages each satisfying 0.ltoreq.x.ltoreq.10, 0.1.ltoreq.y.ltoreq.20, 0.ltoreq.z.ltoreq.20 and 2.ltoreq.w.ltoreq.30, at least 50% of the alloy structure comprising crystal grains of an average grain size of 100 nm or less.

A thin antenna comprising a laminated magnetic core and at least one coil wound around said laminated magnetic core and having a Q-value of 25 or more at 134 kHz, said laminated magnetic core having a thickness of 3 mm or less and being composed of a plurality of magnetic core elements in the form of amorphous alloy strips of a thickness of 25 .mu.m or less having a chemical composition represented by:

• (CO.sub.1-a Fe.sub.a).sub.100-b-c-d-e T.sub.b Si.sub.c B.sub.d Y.sub.c( 1)
• wherein T is at least one element selected from the group consisting of Mn, Ni, Ti, Zr, Hf, Cr, Mo, Nb, W, Ta, Cu, Ru, Rh, Pd, Os, Ir, Pt, Re and Sn;
• Y is at least one element selected from the group consisting of C, Ge, Ga, P and Al;
• a is a numerical value satisfying 0.ltoreq.a.ltoreq.0.1;
• and b, c, d and e are atomic percentages each satisfying 0.ltoreq.b.ltoreq.15, 0.ltoreq.c.ltoreq.20, 5.ltoreq.d.ltoreq.25, 0.ltoreq.e.ltoreq.20 and 15.ltoreq.v+d.ltoreq.30, said magnetic core element being provided with an induced magnetic anisotropy in the width direction or in the thickness direction of said magnetic core.

A thin antenna comprising a laminated magnetic core and at least one coil wound around said laminated magnetic core and having a Q-value of 25 or more at 134 kHz, said laminated magnetic core having a thickness of 3 mm or less and being composed of a plurality of nano-crystalline alloy strips of a thickness of 25 .mu.m or less having a chemical composition represented by:

• (Fe.sub.1-v M.sub.v).sub.100-x-y-z-w A.sub.xM'.sub.y M".sub.z X.sub.w( 2)
• wherein M is Co, Ni or a combination thereof;
• A is Cu, Au or a combination thereof;
• M' is at least one element selected from the group consisting of Ti, V, Zr, Nb, Mo, Hf, Ta and W;
• M" is at least one element selected from the group consisting of Cr, Mn, Al, Sn, Zn, Ag, In, platinum group elements, Mg, Ca, Sr, Y, rare earth elements, N, O and S;
• X is at least one element selected from the group consisting of B, Si, C, Ge, Ga and P;
• v is a numerical value satisfying 0.ltoreq.v.ltoreq.0.5;
• and x, y, z and w are atomic percentages each satisfying 0.ltoreq.x.ltoreq.10, 0.1.ltoreq.y.ltoreq.20, 0.ltoreq.z.ltoreq.20 and 2.ltoreq.w.ltoreq.30, at least 50% of the alloy structure comprising crystal grains of an average grain size of 100 nm or less.