Single-pass recording of multilevel patterned media

Abstract

A method of performing data/information recording and retrieval utilizing a multilevel patterned magnetic medium, comprises: (a) providing a magnetic recording system including a read/write head and a multilevel patterned magnetic recording medium including a plurality of spaced apart elements each comprising a stacked plurality n of magnetic recording cells with different magnetic properties and magnetically decoupled from overlying and/or underlying cells; (b) providing relative movement between the write head and magnetic recording medium; and; (c) writing to the medium by supplying the write head with a modulated write current comprising a plurality n of pulses of different magnitudes while the head moves past each element, thereby applying n different magnetic field strengths to each element, the write current including a first pulse of magnitude sufficient to write to a first cell of each element having a highest magnetic coercivity of said cells, and n−1 succeeding pulses of progressively smaller magnitude for sequentially writing to the remaining n−1 lower magnetic coercivity cells of each element but of insufficient magnitude to write to progressively higher magnetic coercivity cells; whereby the writing occurs in a single pass of the write head past each element.

1 . A method of performing data/information recording and retrieval utilizing a multilevel patterned magnetic medium, comprising steps of:
 (a) providing a magnetic recording system including a multilevel patterned magnetic recording medium and a write head, said medium including a plurality of spaced apart elements, each element comprising a stacked plurality n of magnetic recording cells each with different magnetic properties, each cell magnetically decoupled from overlying and/or underlying cells;   (b) providing relative movement between said write head and a surface of said magnetic recording medium; and   (c) writing to said medium by supplying said write head with a modulated write current comprising a plurality n of pulses of different magnitudes while said head moves past each element, thereby applying n different magnetic field strengths to each element, wherein said modulated write current:   (i) includes a first pulse of magnitude sufficient to write to a first cell of each element having a highest magnetic coercivity of said cells; and   (ii) includes n−1 succeeding pulses of progressively smaller magnitude for sequentially writing to the remaining n−1 lower magnetic coercivity cells of each element but of insufficient magnitude to write to progressively higher magnetic coercivity cells; wherein:   said writing to said medium occurs in a single pass of said write head past each said element.   
     
     
         2 . The method as in  claim 1 , wherein:
 step (a) comprises providing a magnetic recording medium wherein each of said stacked plurality n of magnetic recording cells of each of said elements has the same thermal stability.   
     
     
         3 . The method as in  claim 1 , wherein:
 step (a) comprises providing a magnetic recording medium wherein each of said stacked plurality n of magnetic recording cells of each of said elements is a perpendicular cell including a perpendicular magnetic recording layer.   
     
     
         4 . The method as in  claim 3 , wherein:
 step (a) comprises providing a magnetic recording medium wherein each of said plurality n of perpendicular cells of each element has different magnetic properties determined by the coercivity Hk n , saturation magnetization Ms n , and thickness t n  of its perpendicular magnetic recording layer.   
     
     
         5 . The method as in  claim 4 , wherein:
 step (c) comprises supplying said write head with a modulated write current comprising a plurality n of pulses of different magnitudes in proportion to the magnitudes of the coercivities Hk n  of said perpendicular magnetic recording layers of said plurality n of perpendicular cells.   
     
     
         6 . The method as in  claim 5 , wherein:
 step (a) comprises providing a magnetic recording medium wherein n=2 and each element of said medium includes a first perpendicular cell with a first perpendicular magnetic recording layer with coercivity Hk 1 , saturation magnetization Ms 1 , thickness t 1 , and a second perpendicular cell with a second perpendicular magnetic recording layer with coercivity Hk 2 , saturation magnetization Ms 2 , and thickness t 2 .   
     
     
         7 . The method as in  claim 6 , wherein:
 step (a) comprises providing a magnetic recording medium wherein Hk 2 >Hk 2 ;   and step (c) comprises supplying said write head with modulated current comprising a first, greater magnitude pulse for writing to said first and second perpendicular cells, followed by a second, lesser magnitude pulse for overwriting only said second perpendicular cell.   
     
     
         8 . The method as in  claim 6 , wherein:
 step (a) comprises providing a magnetic recording medium wherein Hk 1 , Ms 1 , t 1  and Hk 2 , Ms 2 , t 2  are selected such that K 1 V 1 =K 2 V 2 , where K 1 V 1 =0.5Hk 1 Ms 1 At 1  and K 2 V 2 =0.5Hk 2 Ms 2 At 2 , wherein K n =magnetic anisotropy, V n =grain volume, and A=cross-sectional area of the stacked cells, whereby said first and second perpendicular cells have the same thermal stability.   
     
     
         9 . The method as in  claim 4 , comprising a further step of:
 (d) reading data/information written to said medium in step (c) by utilizing differences in the product Ms n t n  of the saturation magnetization Ms n  and thickness t n  of the perpendicular magnetic recording layers of each perpendicular cell.   
     
     
         10 . The method as in  claim 1 , wherein:
 step (a) comprises providing a disk-shaped medium.   
     
     
         11 . A multilevel patterned magnetic recording medium, comprising:
 (a) a non-magnetic substrate including a surface; and   (b) a plurality of spaced apart elements on said surface, each element comprising a stacked plurality n of magnetic recording cells each with different magnetic properties, each cell magnetically decoupled from overlying and/or underlying cells; wherein each of said stacked plurality n of magnetic recording cells:   (i) is a perpendicular cell including a perpendicular magnetic recording layer;   (ii) has different magnetic properties determined by the coercivity Hk n , saturation magnetization Ms n , and thickness t n  of its perpendicular magnetic recording layer; and   (iii) Hk n , Ms n , and t n  are selected such that K n V n =0.5Hk n Ms n At n  is equal for each of said n cells, where K n =magnetic anisotropy and V n =grain volume of its perpendicular magnetic recording layer, and A=cross-sectional area of each of said stacked cells, whereby each of said n perpendicular cells has the same thermal stability.   
     
     
         12 . The medium as in  claim 11 , wherein:
 the coercivity Hk n  and Ms n t n  product of the saturation magnetization Ms n  and thickness t n  of each of said perpendicular magnetic recording layers of each said perpendicular cell are different.   
     
     
         13 . The medium according to  claim 11 , wherein:
 said substrate is disk-shaped.   
     
     
         14 . The medium according to  claim 11 , wherein:
 each of said elements is circular column-shaped.   
     
     
         15 . The medium as in  claim 11 , wherein:
 said elements are arranged in a patterned array.   
     
     
         16 . The medium as in  claim 11 , wherein:
 n=2 and each element of said medium includes a first perpendicular cell with a first perpendicular magnetic recording layer with coercivity Hk 1 , saturation magnetization Ms 1 , thickness t 1 , and a second perpendicular cell with a second perpendicular magnetic recording layer with coercivity Hk 2 , saturation magnetization Ms 2 , and thickness t 2 .   
     
     
         17 . The medium as in  claim 16 , wherein:
 Hk 1 ≠Hk 2  and Ms 1 t 1 ≠Ms 2 t 2 .   
     
     
         18 . A magnetic data/information recording and retrieval system, comprising the multilevel patterned magnetic recording medium of  claim 11  and at least one read/write head. 
     
     
         19 . The system according to  claim 18 , wherein said medium is disk-shaped. 
     
     
         20 . The system according to  claim 19 , further comprising a disk drive.