Exchange coupled magnetic elements
Approaches to reduce switching field distribution in energy assisted magnetic storage devices involve first and second exchange coupled magnetic elements. The first magnetic elements have anisotropy, H k1 , volume, V 1 and the second magnetic elements are magnetically exchange coupled to the first magnetic elements and have anisotropy H k2 , and volume V 2 . The thermal stability of the exchange coupled magnetic elements is greater than about 60 k B T at a storage temperature of about 300 K. The magnetic switching field distribution, SFD, of the exchange coupled magnetic elements is less than about 200% at a predetermined magnetic switching field and a predetermined assisting switching energy.
1. A magnetic storage article, comprising:
first magnetic elements having anisotropy, H k1 , volume, V 1 ; and
second magnetic elements magnetically exchange coupled to the first magnetic elements, the second magnetic elements having anisotropy H k2 , and volume V 2 , wherein a thermal stability of the exchange coupled magnetic elements is greater than about 60 k B T at a storage temperature of about 300 K and a magnetic switching field distribution, SFD, of the exchange coupled magnetic elements is less than about 200% at a predetermined magnetic switching field and a predetermined assisting switching energy, wherein the first magnetic elements and the second magnetic elements are disposed in a single layer, the first magnetic elements are laterally adjacent to the second magnetic elements in the layer H k1 ≠H k2 and V 1 ≠V 2 .
2. The article of claim 1 , wherein the assisting switching energy comprises thermal energy.
3. The article of claim 1 , wherein the assisting switching energy comprises microwave magnetic energy.
4. The article of claim 1 , wherein the magnetic storage article comprises heat assisted magnetic recording (HAMR) medium.
5. The article of claim 1 , wherein the magnetic storage article is a microwave assisted magnetic recording (MAMR) medium.
6. The article of claim 1 , wherein the magnetic storage article is magnetoresistive random access memory (MRAM).
7. The article of claim 1 , wherein the magnetic storage article comprises a patterned medium.
8. The magnetic article of claim 1 , wherein each of the first and second magnetic elements have a volume less than about 10,000 nm 3 .
9. The article of claim 1 , wherein the first magnetic elements have a saturation magnetization of M s1 , the second magnetic elements have a saturation magnetization of M s2 , and the ratio M s2 H k2 /M s1 H k1 is less than about 0.8.
10. The article of claim 9 , wherein M s2 is equal to M s1 .
11. The article of claim 1 , wherein the exchange field, h ex =JM s2 /H k1 is less than about 0.65, where J is the exchange coupling strength between the first magnetic elements and the second magnetic elements and M s2 is the magnetization saturation of the second magnetic elements.
12. The article of claim 1 , wherein the single layer is a continuous media layer.
13. The article of claim 12 , wherein:
the second magnetic elements comprise CoPtX or CoCrPtX or CoCrX, where X is at least one additional non-magnetic metallic or non-metallic material; and
the first magnetic elements comprise FePtX or CoPtX, where X is at least one additional non-magnetic metallic or non-metallic material, with L1 0 structure.
14. The article of claim 1 , wherein the second magnetic elements have a Curie temperature, T c2 , and T c2 is not equal to a Curie temperature of the first magnetic elements, T c1 .