1. An MRAM structure, comprising:
(a) a magnetic tunnel junction (MTJ) sensing element having length and width dimensions and formed on a conductive substrate, said MTJ has a first stack of layers comprised of a ferromagnetic layer with a magnetization direction along a first axis, a super-paramagnetic (SP) free layer in which a remnant magnetization is substantially zero in the absence of an external field, and in which magnetization is roughly proportional to an external field until reaching a saturation value, and an insulating layer formed between the ferromagnetic layer and SP free layer; and
(b) a storage layer having anisotropy and an easy axis.
2. The MRAM structure of claim 1 wherein the SP free layer has a thickness between about 5 and 20 Angstroms and is comprised of multiple layers or laminated layers of Co, Fe, Ni, CoFe, NiFe, CoFeNi, or having a composition represented by CoXFeYBZ wherein x, y, and z are the atomic % of Co, Fe, and B, respectively, x+y+z=100, x is about 40 to 60, y is from about 15 to 30, and z is from about 12.5 to 25.
3. The MRAM structure of claim 1 wherein said ferromagnetic layer is a pinned layer having a synthetic anti-parallel (SyAP) configuration.
4. The MRAM structure of claim 1 wherein said insulating layer is comprised of an oxide which is AlOx, TiOx, HfOx, MgO, or a lamination of one or more of the aforementioned oxides.
5. The MRAM structure of claim 1 wherein said insulating layer is comprised of a nitride which is AlNx, TiNx, HfNx, MgNx, or a lamination of one or more of the aforementioned nitrides.
6. The MRAM structure of claim 1 wherein said storage layer is ferromagnetic or ferrimagnetic and has an anisotropy substantially along the first axis and in the same direction as that of the magnetic moment of said ferromagnetic layer in the MTJ.
7. The MRAM structure of claim 1 wherein said anisotropy is a shape anisotropy resulting from an elliptical, rectangular, eye, or diamond shape and the magnetization direction of the storage layer is oriented along its easy axis which is parallel to the magnetization direction of the ferromagnetic layer in the MTJ.
8. The MRAM structure of claim 1 wherein the storage layer is formed above, below or adjacent to the MTJ and has a lengthwise dimension along said easy axis that is greater than the width dimension of the MTJ.
9. The MRAM structure of claim 1 wherein the storage layer has a uniaxial crystalline anisotropy.
10. The MRAM structure of claim 1 wherein the storage layer is about 20 to 50 Angstroms thick and is formed on a non-magnetic conducting spacer layer, said storage layer and non-magnetic spacer are incorporated in the MTJ such that the storage layer and non-magnetic spacer have essentially the same shape, and same length and width dimensions as the MTJ element from a top-down perspective.
11. The MRAM structure of claim 10 wherein the non-magnetic spacer layer is comprised of Ta, Cu, Ru, Au, Ag, Zr, Rh, Cr, W, or alloys or multilayers thereof and has a thickness of about 5 to 300 Angstroms.
12. The MRAM structure of claim 10 wherein the MTJ is further comprised of a cap layer as the uppermost layer in the MTJ and wherein the storage layer and non-magnetic spacer form a second stack of layers and said second stack is formed between the first stack and the cap layer.
13. The MRAM structure of claim 10 wherein the MTJ is further comprised of a seed layer on which the first stack is formed and wherein the storage layer and non-magnetic spacer form a second stack of layers and said second stack is formed between the conductive substrate and the seed layer.
14. A method of forming a MTJ element in a MRAM structure, comprising:
(a) depositing a seed layer on a conductive substrate;
(b) forming a first stack on said seed layer, said first stack is comprised of a pinned layer, a super-paramagnetic (SP) free layer, a insulator layer between the pinned layer and SP free layer, and an AFM layer on a surface of the pinned layer opposite the insulating layer;
(c) forming a second stack on the first stack, said second stack is comprised of a lower non-magnetic conducting spacer layer and an upper storage layer; and
(d) forming a cap layer on said second stack.
15. The method of claim 14 wherein the SP free layer has a thickness between about 5 and 20 Angstroms and is comprised of a ferromagnetic material which is CoFeB, Co, Fe, Ni, CoFe, NiFe, or CoFeNi.
16. The method of claim 14 wherein said insulating layer is comprised of AlOx, TiOx, HfOx, MgO, or a lamination of one or more of the aforementioned oxides or is made of AlNx, TiNx, HfNx, MgNx or a lamination of one or more of the aforementioned nitrides.
17. The method of claim 14 wherein said storage layer is ferromagnetic or ferrimagnetic and has a uniaxial anisotropy substantially along a first axis and in the same direction as that of the pinned layer.
18. The method of claim 17 wherein said ferromagnetic or ferrimagnetic storage layer is pinned by an AFM layer.
19. The method of claim 14 wherein the non-magnetic conducting spacer layer is comprised of Ta, Cu, Ru, Au, Ag, Zr, Rh, Cr, W, or alloys or multilayers thereof and has a thickness of about 5 to 300 Angstroms.
20. The method of claim 14 wherein the storage layer is a synthetic ferromagnetic layer with a synthetic anti-parallel (SyAP) configuration.
21. The method of claim 14 wherein the storage layer is a lamination of one or more ferromagnetic layers andor one or more ferrimagnetic layers.
22. A method of forming a MTJ element in a MRAM structure, comprising:
(a) forming a first stack comprised of a lower non-magnetic conducting spacer layer and an upper storage layer on a conductive substrate;
(b) depositing a seed layer on said first stack;
(c) forming a second stack on said seed layer wherein said second stack is comprised of a pinned layer, a super-paramagnetic (SP) free layer, a insulator layer between the pinned layer and SP free layer, and an AFM layer on a surface of the pinned layer opposite the insulating layer; and
(d) forming a cap layer on said second stack.
23. The method of claim 22 wherein the SP free layer has a thickness between about 5 and 20 Angstroms and is comprised of a ferromagnetic material which is CoFeB, Co, Fe, Ni, CoFe, NiFe, or CoFeNi.
24. The method of claim 22 wherein said insulating layer is comprised of AlOx, TiOx, HfOx, MgO, or a lamination of one or more of the aforementioned oxides or is made of AlNx, TiNx, HfNx, MgNx or a lamination of one or more of the aforementioned nitrides.
25. The method of claim 22 wherein said storage layer is ferromagnetic or ferrimagnetic and has a uniaxial anisotropy substantially along a first axis and in the same direction as that of the pinned layer.
26. The method of claim 22 wherein said ferromagnetic or ferrimagnetic storage layer is pinned by an AFM layer.
27. The method of claim 22 wherein the non-magnetic conducting spacer layer is comprised of Ta, Cu, Ru, Au, Ag, Zr, Rh, Cr, W, or alloys or multilayers thereof and has a thickness of about 50 to 300 Angstroms.
28. The method of claim 22 wherein the storage layer is a synthetic ferromagnetic layer with a synthetic anti-parallel (SyAP) configuration.
29. The method of claim 22 wherein the storage layer is a lamination of one or more ferromagnetic layers andor one or more ferromagnetic layers.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. An antenna device comprising:
an antenna having a single feed;
a shunt circuit including:
a first shunt matching circuit configured to cause impedance, viewed from a main path connecting the antenna and a radio frequency circuit, to be substantially infinite with respect to all frequency ranges handled by the antenna; and
a second shunt matching circuit configured to provide a predetermined impedance characteristic with respect to a first subset of the frequency ranges handled by the antenna,
wherein a first end of each of the first and second shunt matching circuits are connected to ground, and a second end of each of the first and second shunt matching circuits are selectively connected to the main path; and
a selection controller configured to control selection of which of the first and second shunt matching circuits are connected to the main path.
2. The antenna device of claim 1, further comprising:
a first filter provided between the main path and the shunt circuit and configured to allow passage of only the first subset of the frequency ranges.
3. The antenna device of claim 2, further comprising:
a series circuit including a plurality of series matching circuits, each configured to provide a predetermined impedance characteristic with respect to a second subset of the frequency ranges handled by the antenna,
wherein the series circuit is configured to selectively connect each of the plurality of series matching circuits in parallel with the main path.
4. The antenna device of claim 3, wherein the selection controller is configured to control selection of which of the plurality of series matching circuits are connected in parallel with the main path.
5. The antenna device of claim 3, further comprising:
a second filter provided between the main path and the series circuit configured to allow passage of only the second subset of the frequency ranges.
6. The antenna device of claim 1, wherein, when a second subset of the frequency ranges handled by the antenna are to be used, the selection controller controls selection of the first shunt matching circuit to be connected to the main path.
7. The antenna device of claim 1, further comprising:
a main matching circuit connected in series with the main path and configured to provide a predetermined impedance characteristic with respect to a predetermined subset of the frequency ranges handled by the antenna.
8. The antenna device of claim 7, wherein when the frequency range used is the predetermined subset of the frequency ranges, the selection controller controls selection of the first shunt matching circuit to be connected to the main path.
9. The antenna device of claim 8, further comprising:
a filter unit provided in the main path closer to the radio frequency circuit than the main matching circuit, and configured to allow passage of only the first subset of the frequency ranges when the predetermined frequency range is included in the first subset of the frequency ranges.
10. The antenna device of claim 1, further comprising:
a phase shifter connected in series with the main path and configured to adjust a phase of a signal passing through the main path.
11. The antenna device of claim 5, wherein the shunt circuit and the first filter are provided closer to the antenna on the main path than the series circuit and the second filter.
12. The antenna device of claim 5, wherein the shunt circuit and the first filter are provided closer to the radio frequency circuit on the main path than the series circuit and the second filter.
13. The antenna device of claim 3, further comprising:
an integrated switch configured to cause the first and second shunt matching circuits to be selectively connected to the main path, and to cause the series matching circuits to be selectively connected to the main path.
14. The antenna device of claim 3, wherein the first subset of the frequency ranges is lower in frequency than the second subset of the frequency ranges.
15. The antenna device of claim 3, wherein the first subset of the frequency ranges is higher in frequency than the second subset of the frequency ranges.
16. A radio communication apparatus comprising:
an antenna device including:
an antenna having a single feed;
a shunt circuit including:
a first shunt matching circuit configured to cause impedance, viewed from a main path connecting the antenna and a radio frequency circuit, to be substantially infinite with respect to all frequency ranges handled by the antenna; and
a second shunt matching circuit configured to provide a predetermined impedance characteristic with respect to a first subset of the frequency ranges handled by the antenna,
wherein a first end of each of the first and second shunt matching circuits are connected to ground, and a second end of each of the first and second shunt matching circuits are selectively connected to the main path; and
a selection controller configured to control selection of which of the first and second shunt matching circuits are connected to the main path.
17. An antenna device comprising:
an antenna having a single feed;
a shunt circuit including:
means for causing impedance, viewed from a main path connecting the antenna and a radio frequency circuit, to be substantially infinite with respect to all frequency ranges handled by the antenna; and
means for providing a predetermined impedance characteristic with respect to a first subset of the frequency ranges handled by the antenna,
wherein the means for causing and means for providing are selectively connected to the main path; and
means for controlling selection of which of the means for providing and means for causing are connected to the main path.