Exchange Coupled Magnetic Elements

Abstract

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.   
     
     
         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 grains and the second grains and M s2  is the magnetization saturation of the second grains. 
     
     
         12 . The article of  claim 1 , wherein the first and second grains are disposed in a single layer. 
     
     
         13 . A magnetic storage article, comprising:
 a first magnetic recording layer including first magnetic elements with anisotropy, H k1 , volume, V 1 ; and   a second magnetic recording layer including 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 switching temperature of greater than about 350 K.   
     
     
         14 . The article of  claim 13 , wherein the first and second layers are continuous media layers. 
     
     
         15 . The article of  claim 14 , wherein:
 the second grains comprise CoPtX or CoCrPtX or CoCrX, where X is a non-magnetic metallic or non-metallic material; and   the first grains comprise FePtX or CoPtX with L1 0  structure.   
     
     
         16 . The article of  claim 14 , wherein an exchange coupling layer is disposed between the first layer and the second layer. 
     
     
         17 . The article of  claim 14 , wherein the exchange coupling layer comprises MgO, Mg, or Ag. 
     
     
         18 . The article of  claim 13 , 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 . 
     
     
         19 . The article of  claim 13 , wherein each of the first and second magnetic elements have a volume less than about 10,000 nm 3 . 
     
     
         20 . The article of  claim 13 , wherein H k1  is about equal to H k2 , an aspect ratio of the first and second magnetic elements is substantially the same, and V 1  is not equal to V 2 .