<s>
Magnetic	B-Architecture
storage	I-Architecture
or	O
magnetic	B-Architecture
recording	I-Architecture
is	O
the	O
storage	O
of	O
data	O
on	O
a	O
magnetized	O
medium	O
.	O
</s>
<s>
Magnetic	B-Architecture
storage	I-Architecture
uses	O
different	O
patterns	O
of	O
magnetisation	O
in	O
a	O
magnetizable	O
material	O
to	O
store	O
data	O
and	O
is	O
a	O
form	O
of	O
non-volatile	B-General_Concept
memory	I-General_Concept
.	O
</s>
<s>
The	O
information	O
is	O
accessed	O
using	O
one	O
or	O
more	O
read/write	B-Device
heads	I-Device
.	O
</s>
<s>
Magnetic	B-Architecture
storage	I-Architecture
media	O
,	O
primarily	O
hard	B-Device
disks	I-Device
,	O
are	O
widely	O
used	O
to	O
store	O
computer	B-General_Concept
data	I-General_Concept
as	O
well	O
as	O
audio	O
and	O
video	O
signals	O
.	O
</s>
<s>
In	O
the	O
field	O
of	O
computing	O
,	O
the	O
term	O
magnetic	B-Architecture
storage	I-Architecture
is	O
preferred	O
and	O
in	O
the	O
field	O
of	O
audio	O
and	O
video	O
production	O
,	O
the	O
term	O
magnetic	B-Architecture
recording	I-Architecture
is	O
more	O
commonly	O
used	O
.	O
</s>
<s>
Other	O
examples	O
of	O
magnetic	B-Architecture
storage	I-Architecture
media	O
include	O
floppy	B-Device
disks	I-Device
,	O
magnetic	O
tape	O
,	O
and	O
magnetic	O
stripes	O
on	O
credit	O
cards	O
.	O
</s>
<s>
Magnetic	B-Architecture
storage	I-Architecture
in	O
the	O
form	O
of	O
wire	O
recording	O
—	O
audio	O
recording	O
on	O
a	O
wire	O
—	O
was	O
publicized	O
by	O
Oberlin	O
Smith	O
in	O
the	O
Sept	O
8	O
,	O
1888	O
issue	O
of	O
Electrical	O
World	O
.	O
</s>
<s>
Early	O
magnetic	B-Architecture
storage	I-Architecture
devices	O
were	O
designed	O
to	O
record	O
analog	O
audio	O
signals	O
.	O
</s>
<s>
Computers	O
and	O
now	O
most	O
audio	O
and	O
video	O
magnetic	B-Architecture
storage	I-Architecture
devices	O
record	O
digital	B-General_Concept
data	I-General_Concept
.	O
</s>
<s>
In	O
computers	O
,	O
magnetic	B-Architecture
storage	I-Architecture
was	O
also	O
used	O
for	O
primary	O
storage	O
in	O
a	O
form	O
of	O
magnetic	B-General_Concept
drum	I-General_Concept
,	O
or	O
core	B-General_Concept
memory	I-General_Concept
,	O
core	B-General_Concept
rope	I-General_Concept
memory	I-General_Concept
,	O
thin	B-General_Concept
film	I-General_Concept
memory	I-General_Concept
,	O
twistor	B-General_Concept
memory	I-General_Concept
or	O
bubble	B-General_Concept
memory	I-General_Concept
.	O
</s>
<s>
The	O
read-and-write	B-Device
head	I-Device
is	O
used	O
to	O
detect	O
and	O
modify	O
the	O
magnetisation	O
of	O
the	O
material	O
immediately	O
under	O
it	O
.	O
</s>
<s>
In	O
older	O
hard	B-Device
disk	I-Device
drive	I-Device
(	O
HDD	B-Device
)	O
designs	O
the	O
regions	O
were	O
oriented	O
horizontally	O
and	O
parallel	O
to	O
the	O
disk	B-Device
surface	O
,	O
but	O
beginning	O
about	O
2005	O
,	O
the	O
orientation	O
was	O
changed	O
to	O
perpendicular	B-Device
to	O
allow	O
for	O
closer	O
magnetic	O
domain	O
spacing	O
.	O
</s>
<s>
Older	O
hard	B-Device
disk	I-Device
drives	I-Device
used	O
iron(III )	O
oxide	O
(	O
Fe2O3	O
)	O
as	O
the	O
magnetic	O
material	O
,	O
but	O
current	O
disks	B-Device
use	O
a	O
cobalt-based	O
alloy	O
.	O
</s>
<s>
Later	O
development	O
made	O
use	O
of	O
spintronics	O
;	O
in	O
read	O
heads	O
,	O
the	O
magnetoresistive	O
effect	O
was	O
much	O
greater	O
than	O
in	O
earlier	O
types	O
,	O
and	O
was	O
dubbed	O
"	B-General_Concept
giant	I-General_Concept
"	I-General_Concept
magnetoresistance	I-General_Concept
(	O
GMR	B-General_Concept
)	O
.	O
</s>
<s>
The	O
read	O
element	O
is	O
typically	O
magneto-resistive	B-General_Concept
while	O
the	O
write	O
element	O
is	O
typically	O
thin-film	O
inductive	O
.	O
</s>
<s>
The	O
most	O
commonly-used	O
of	O
these	O
was	O
ferric	O
oxide	O
,	O
though	O
chromium	O
dioxide	O
,	O
cobalt	B-Algorithm
,	O
and	O
later	O
pure	O
metal	O
particles	O
were	O
also	O
used	O
.	O
</s>
<s>
Examples	O
of	O
digital	O
recording	O
are	O
floppy	B-Device
disks	I-Device
and	O
hard	B-Device
disk	I-Device
drives	I-Device
(	O
HDDs	O
)	O
.	O
</s>
<s>
Recording	O
media	O
in	O
HDDs	O
use	O
a	O
stack	O
of	O
thin	O
films	O
to	O
store	O
information	O
and	O
a	O
read/write	B-Device
head	I-Device
to	O
read	O
and	O
write	O
information	O
to	O
and	O
from	O
the	O
media	O
;	O
various	O
developments	O
have	O
been	O
carried	O
out	O
in	O
the	O
area	O
of	O
used	O
materials	O
.	O
</s>
<s>
When	O
writing	O
,	O
the	O
magnetic	B-Architecture
medium	I-Architecture
is	O
heated	O
locally	O
by	O
a	O
laser	O
,	O
which	O
induces	O
a	O
rapid	O
decrease	O
of	O
coercive	O
field	O
.	O
</s>
<s>
The	O
magnetic	B-Architecture
medium	I-Architecture
are	O
typically	O
amorphous	O
R-Fe-Co	O
thin	O
film	O
(	O
R	O
being	O
a	O
rare	O
earth	O
element	O
)	O
.	O
</s>
<s>
Domain	O
propagation	O
memory	O
is	O
also	O
called	O
bubble	B-General_Concept
memory	I-General_Concept
.	O
</s>
<s>
The	O
basic	O
idea	O
is	O
to	O
control	O
domain	O
wall	O
motion	O
in	O
a	O
magnetic	B-Architecture
medium	I-Architecture
that	O
is	O
free	O
of	O
microstructure	O
.	O
</s>
<s>
Magnetic	B-Architecture
storage	I-Architecture
media	O
can	O
be	O
classified	O
as	O
either	O
sequential	B-General_Concept
access	I-General_Concept
memory	I-General_Concept
or	O
random	B-Architecture
access	I-Architecture
memory	I-Architecture
,	O
although	O
in	O
some	O
cases	O
the	O
distinction	O
is	O
not	O
perfectly	O
clear	O
.	O
</s>
<s>
In	O
the	O
case	O
of	O
magnetic	O
wire	O
,	O
the	O
read/write	B-Device
head	I-Device
only	O
covers	O
a	O
very	O
small	O
part	O
of	O
the	O
recording	O
surface	O
at	O
any	O
given	O
time	O
.	O
</s>
<s>
Hard	B-Device
disks	I-Device
and	O
modern	O
linear	O
serpentine	O
tape	O
drives	O
do	O
not	O
precisely	O
fit	O
into	O
either	O
category	O
.	O
</s>
<s>
Both	O
have	O
many	O
parallel	O
tracks	O
across	O
the	O
width	O
of	O
the	O
media	O
and	O
the	O
read/write	B-Device
heads	I-Device
take	O
time	O
to	O
switch	O
between	O
tracks	O
and	O
to	O
scan	O
within	O
tracks	O
.	O
</s>
<s>
For	O
a	O
hard	B-Device
disk	I-Device
this	O
time	O
is	O
typically	O
less	O
than	O
10	O
ms	O
,	O
but	O
tapes	O
might	O
take	O
as	O
much	O
as	O
100	O
s	O
.	O
</s>
<s>
Magnetic	B-Architecture
disk	I-Architecture
heads	O
and	O
magnetic	O
tape	O
heads	O
cannot	O
pass	O
DC	O
(	O
direct	O
current	O
)	O
,	O
so	O
the	O
coding	O
schemes	O
for	O
both	O
tape	O
and	O
disk	B-Device
data	O
are	O
designed	O
to	O
minimize	O
the	O
DC	O
offset	O
.	O
</s>
<s>
Most	O
magnetic	B-Architecture
storage	I-Architecture
devices	O
use	O
error	B-Error_Name
correction	I-Error_Name
.	O
</s>
<s>
Many	O
magnetic	B-Architecture
disks	I-Architecture
internally	O
use	O
some	O
form	O
of	O
run-length	B-Protocol
limited	I-Protocol
coding	I-Protocol
and	O
partial-response	B-Device
maximum-likelihood	I-Device
.	O
</s>
<s>
,	O
common	O
uses	O
of	O
magnetic	B-Architecture
storage	I-Architecture
media	O
are	O
for	O
computer	B-General_Concept
data	I-General_Concept
mass	O
storage	O
on	O
hard	B-Device
disks	I-Device
and	O
the	O
recording	O
of	O
analog	O
audio	O
and	O
video	O
works	O
on	O
analog	O
tape	O
.	O
</s>
<s>
Since	O
much	O
of	O
audio	O
and	O
video	O
production	O
is	O
moving	O
to	O
digital	O
systems	O
,	O
the	O
usage	O
of	O
hard	B-Device
disks	I-Device
is	O
expected	O
to	O
increase	O
at	O
the	O
expense	O
of	O
analog	O
tape	O
.	O
</s>
<s>
Digital	B-Architecture
tape	I-Architecture
and	O
tape	B-Device
libraries	I-Device
are	O
popular	O
for	O
the	O
high	O
capacity	O
data	O
storage	O
of	O
archives	O
and	O
backups	O
.	O
</s>
<s>
Floppy	B-Device
disks	I-Device
see	O
some	O
marginal	O
usage	O
,	O
particularly	O
in	O
dealing	O
with	O
older	O
computer	O
systems	O
and	O
software	O
.	O
</s>
<s>
Magnetic	B-Architecture
storage	I-Architecture
is	O
also	O
widely	O
used	O
in	O
some	O
specific	O
applications	O
,	O
such	O
as	O
bank	O
cheques	O
(	O
MICR	O
)	O
and	O
credit/debit	O
cards	O
(	O
mag	O
stripes	O
)	O
.	O
</s>
<s>
A	O
new	O
type	O
of	O
magnetic	B-Architecture
storage	I-Architecture
,	O
called	O
magnetoresistive	B-General_Concept
random-access	I-General_Concept
memory	I-General_Concept
or	O
MRAM	B-General_Concept
,	O
is	O
being	O
produced	O
that	O
stores	O
data	O
in	O
magnetic	O
bits	O
based	O
on	O
the	O
tunnel	O
magnetoresistance	O
(	O
TMR	O
)	O
effect	O
.	O
</s>
<s>
Its	O
advantage	O
is	O
non-volatility	B-General_Concept
,	O
low	O
power	O
usage	O
,	O
and	O
good	O
shock	O
robustness	O
.	O
</s>
<s>
The	O
2nd	O
generation	O
is	O
being	O
developed	O
through	O
two	O
approaches	O
:	O
thermal-assisted	B-General_Concept
switching	I-General_Concept
(	O
TAS	O
)	O
which	O
is	O
currently	O
being	O
developed	O
by	O
Crocus	O
Technology	O
,	O
and	O
spin-transfer	B-General_Concept
torque	I-General_Concept
(	O
STT	O
)	O
on	O
which	O
Crocus	O
,	O
Hynix	O
,	O
IBM	O
,	O
and	O
several	O
other	O
companies	O
are	O
working	O
.	O
</s>
<s>
However	O
,	O
with	O
storage	O
density	O
and	O
capacity	O
orders	O
of	O
magnitude	O
smaller	O
than	O
an	O
HDD	B-Device
,	O
MRAM	B-General_Concept
is	O
useful	O
in	O
applications	O
where	O
moderate	O
amounts	O
of	O
storage	O
with	O
a	O
need	O
for	O
very	O
frequent	O
updates	O
are	O
required	O
,	O
which	O
flash	B-Device
memory	I-Device
cannot	O
support	O
due	O
to	O
its	O
limited	O
write	O
endurance	O
.	O
</s>
<s>
Six	O
state	O
MRAM	B-General_Concept
is	O
also	O
being	O
developed	O
,	O
echoing	O
four	O
bit	O
multi	O
level	O
flash	B-Device
memory	I-Device
cells	O
,	O
that	O
have	O
six	O
different	O
bits	O
,	O
as	O
opposed	O
to	O
two	O
.	O
</s>
<s>
Research	O
is	O
also	O
being	O
done	O
by	O
Aleksei	O
Kimel	O
at	O
Radboud	O
University	O
in	O
the	O
Netherlands	O
towards	O
the	O
possibility	O
of	O
using	O
terahertz	B-Architecture
radiation	I-Architecture
rather	O
than	O
using	O
standard	O
electropulses	O
for	O
writing	O
data	O
on	O
magnetic	B-Architecture
storage	I-Architecture
media	O
.	O
</s>
<s>
By	O
using	O
terahertz	B-Architecture
radiation	I-Architecture
,	O
writing	O
time	O
can	O
be	O
reduced	O
considerably	O
(	O
50x	O
faster	O
than	O
when	O
using	O
standard	O
electropulses	O
)	O
.	O
</s>
<s>
Another	O
advantage	O
is	O
that	O
terahertz	B-Architecture
radiation	I-Architecture
generates	O
almost	O
no	O
heat	O
,	O
thus	O
reducing	O
cooling	O
requirements	O
.	O
</s>
