US 11,386,320 B2Granted

Magnetic domain wall-based non-volatile, linear and bi-directional synaptic weight element

AssigneeInternational Business Machines Corporation

InventorsAakash Pushp, Pritish Narayanan

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Abstract

A magnetic double tunnel junction (MDTJ) (which, preferably, has a large aspect ratio, wherein length L of the MDTJ>>width w of the MDTJ) has magnetic domain wall(s) or DW(s) in the free layer of the MDTJ, wherein controlled movement of the DW(s) across the free layer is effected in response to the polarity, magnitude, and duration of a voltage pulse across the MDTJ. The motion and relative position of DW(s) causes the conductance of the MDTJ (that is measured across the MDTJ) to change in a symmetric and linear fashion. By reversing the polarity of the bias voltage, the creation and/or direction of the DW(s) motion can be reversed, thereby allowing for a bi-directional response to the input pulse.

Claims36

Dependent claims

A method of adjusting conductance of a synaptic weight element,

the synaptic weight element comprising:
an upper electrical contact;
a first magnetic reference layer directly underlying the upper electrical contact;
a first insulating tunnel barrier directly underlying the first magnetic reference layer;
a magnetic free layer directly underlying the first insulating tunnel barrier;
a second insulating tunnel barrier directly underlying the magnetic free layer;
a second magnetic reference layer directly underlying the second insulating tunnel barrier, and a lower electrical contact directly underlying the second magnetic reference layer, the first and second insulating tunnel barriers having different electrical resistance;
the method comprising:
when the conductance of the synaptic weight element is to be increased, applying a first bias voltage V between the upper electrical contact and the lower electrical contact, so that the first bias voltage V induces a first voltage V1 across the first insulating tunnel barrier and induces a second voltage V2 across the second insulating tunnel barrier, wherein V=V1+V2 and V1≠V2, wherein the first bias voltage V creates and/or moves at least one magnetic domain wall in the magnetic free layer in a first direction, wherein creation and/or movement of the at least one magnetic domain wall in the first direction increases the conductance of the synaptic weight element;
and
when the conductance of the synaptic weight element is to be decreased, applying a second bias voltage V′ between the upper electrical contact and the lower electrical contact, the second bias voltage V′ being opposite in polarity to that of the first bias voltage V, the second bias voltage V′ inducing a third voltage V3 across the first insulating tunnel barrier and inducing a fourth voltage V4 across the second insulating tunnel barrier, wherein V′=V3+V4 and V3≠V4, and the second bias voltage V′ creates and/or moves at least one magnetic domain wall in the magnetic free layer in a second direction that is opposite that of the first direction, and wherein creation and/or movement of the at least one magnetic domain wall in the second direction decreases the conductance of the synaptic weight element.

8 more elements

A method of adjusting conductance of a synaptic weight element,

the synaptic weight element comprising:
an upper electrical contact;
a first magnetic reference layer directly underlying the upper electrical contact;
a first insulating tunnel barrier directly underlying the first magnetic reference layer;
a magnetic free layer directly underlying the first insulating tunnel barrier;
a second insulating tunnel barrier directly underlying the magnetic free layer;
a second magnetic reference layer directly underlying the second insulating tunnel barrier, and a lower electrical contact directly underlying the second magnetic reference layer, the first and second insulating tunnel barriers of different electrical resistance;
the method comprising:
when the conductance of the synaptic weight element is to be decreased, applying a first bias voltage V between the upper electrical contact and the lower electrical contact, so that the voltage V induces a first current I1 travelling from the upper electrical contact to the lower electrical contact, the first bias voltage V creating and/or moving at least one magnetic domain wall in the magnetic free layer in a first direction, wherein creation and/or movement of the at least one magnetic domain wall in the first direction decreases the conductance of the synaptic weight element;
and
when the conductance of the synaptic weight element is to be increased, applying a second bias voltage V′ between the upper electrical contact and the lower electrical contact, the second bias voltage V′ being opposite in polarity to that of the first bias voltage V, the second bias voltage V′ inducing a second current I2 travelling from the lower electrical contact to the upper electrical contact, wherein the second bias voltage V′ creates and/or moves at least one magnetic domain wall in the magnetic free layer in a second direction that is opposite that of the first direction, and wherein creation and/or movement of the at least one magnetic domain wall in the second direction increases the conductance of the synaptic weight element.

8 more elements

Dependencies are inferred from the claim text.

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Abstract

A method of adjusting conductance of a synaptic weight element,

the synaptic weight element comprising:
an upper electrical contact;
a first magnetic reference layer directly underlying the upper electrical contact;
a first insulating tunnel barrier directly underlying the first magnetic reference layer;
a magnetic free layer directly underlying the first insulating tunnel barrier;
a second insulating tunnel barrier directly underlying the magnetic free layer;
a second magnetic reference layer directly underlying the second insulating tunnel barrier, and a lower electrical contact directly underlying the second magnetic reference layer, the first and second insulating tunnel barriers having different electrical resistance;
the method comprising:
when the conductance of the synaptic weight element is to be increased, applying a first bias voltage V between the upper electrical contact and the lower electrical contact, so that the first bias voltage V induces a first voltage V1 across the first insulating tunnel barrier and induces a second voltage V2 across the second insulating tunnel barrier, wherein V=V1+V2 and V1≠V2, wherein the first bias voltage V creates and/or moves at least one magnetic domain wall in the magnetic free layer in a first direction, wherein creation and/or movement of the at least one magnetic domain wall in the first direction increases the conductance of the synaptic weight element;
and
when the conductance of the synaptic weight element is to be decreased, applying a second bias voltage V′ between the upper electrical contact and the lower electrical contact, the second bias voltage V′ being opposite in polarity to that of the first bias voltage V, the second bias voltage V′ inducing a third voltage V3 across the first insulating tunnel barrier and inducing a fourth voltage V4 across the second insulating tunnel barrier, wherein V′=V3+V4 and V3≠V4, and the second bias voltage V′ creates and/or moves at least one magnetic domain wall in the magnetic free layer in a second direction that is opposite that of the first direction, and wherein creation and/or movement of the at least one magnetic domain wall in the second direction decreases the conductance of the synaptic weight element.

8 more elements