Device and method for high speed metamagnetic resistive switching

1 . A device for high speed metamagnetic resistive switching, comprising:

a substrate;

first and second terminals formed on said substrate; and,

at least one metamagnetic phase transitioning (MPT) portion formed on said substrate, said MPT portion being coupled to said first and second terminals to define an electrical conduction path in resistivity adjustable manner therebetween;

wherein said MPT portion is selectively tuned for temperature-responsive phase transitions bidirectionally between predetermined first and second magnetic phases through an intermediate phase, first and second phase boundaries being defined between the intermediate phase and the first and second magnetic phases respectively, the first and second phase boundaries each being traversed at different critical temperatures depending on direction of traversal, the different critical temperatures for each of the first and second phase boundaries being mutually offset by a hysteretic shift;

wherein said MPT portion is boosted in magnetic phase across the first phase boundary responsive to thermal actuation pulsed in a first direction to reach or exceed both the critical temperatures of the first phase boundary in the first direction, and across the second phase boundary responsive to thermal actuation pulsed in a second direction to reach or exceed both the different critical temperatures of the second phase boundary in the second direction, the electrical conduction path of said MPT portion being thereby adjusted in resistivity for switching between ON and OFF states; and,

wherein the pulsed thermal actuation includes pulsed energization applied across said first and second terminals, the pulsed energization being adaptively tuned in amplitude to define separately adjusted peak amplitudes in the first and second directions relative to a predetermined baseline amplitude, said MPT portion at the predetermined baseline amplitude being biased to the intermediate phase, whereby the peak amplitudes may be different in the first and second directions depending on the predetermined baseline amplitude.

2 . The device as recited in claim 1 , wherein:

said MPT portion is switched from an OFF state to an ON state responsive to thermal actuation pulsed to raise said MPT portion in temperature up to at least the higher of the critical temperatures for one of the first and second boundaries, and switched from the ON state to the OFF state responsive to thermal actuation pulsed to lower said MPT portion in temperature down to at least the lower of the critical temperatures for the other of the first and second boundaries; and,

said MPT portion in the first magnetic phase substantially defines an antiferromagnetic (AFM) domain and in the second magnetic phase substantially defines a ferromagnetic (FM) domain; and, said MPT portion varies in resistivity through the intermediate phase in substantially linear response to variation in temperature, said MPT having different resistivity values mutually offset by a hysteretic shift depending on direction of magnetic phase transition into the intermediate phase.

3 . The device as recited in claim 2 , wherein said MPT portion is formed substantially of a metallic material.

4 . The device as recited in claim 3 , wherein the metallic material of said MPT portion includes an FeRh material.

5 . The device as recited in claim 4 , wherein the critical temperature for traversal is greater at each of the first and second phase boundaries for a rising direction of temperature change towards the FM phase than for a lowering direction of temperature change towards the AFM phase.

6 . The device as recited in claim 4 , wherein the pulsed energization includes resistive heating by applying a pulsed voltage signal between said first and second terminals coupled to said MPT portion.

7 . The device as recited in claim 1 , wherein said MPT portion is selectively tunable in phase transitioning response based on at least one of a plurality of predetermined tuning parameters including substitutional doping, material strain, and geometric patterning.

8 . The device as recited in claim 1 , wherein said MPT portion is configured to retain the electrical conduction path in one of the ON and OFF states when stabilized in temperature to remain magnetically within the intermediate phase.

9 . A two terminal switching device having high speed metamagnetic resistive switching between predetermined ON and OFF states for memory, comprising:

a substrate;

first and second terminals formed on said substrate; and,

at least one metamagnetic phase transitioning (MPT) portion formed on said substrate, said MPT portion being formed of a metallic material and coupled to said first and second terminals to define an electrical conduction path in resistivity adjustable manner therebetween;

wherein said MPT portion is selectively tuned for temperature-responsive bidirectional transitions in phase between antiferromagnetic (AFM) and ferromagnetic (FM) phases through an intermediate phase, a first phase boundary being defined between the AFM phase and the intermediate phase and a second phase boundary between the intermediate phase and the FM phase, the first and second phase boundaries each being traversed at different critical temperatures depending on direction of traversal, the different critical temperatures for each of the first and second phase boundaries being mutually offset by a hysteretic shift;

wherein said MPT portion is driven in magnetic phase between the intermediate and FM phases to switch the electrical conduction path in resistivity from the OFF state to the ON state responsive to pulsed energization for raising said MPT portion in temperature up to at least the higher of the critical temperatures for the second boundary, said MPT portion being driven in magnetic phase between the intermediate and AFM phases to switch the electrical conduction path in resistivity from the ON state to the OFF state responsive to pulsed energization for lowering said MPT portion in temperature down to at least the lower of the critical temperatures for the first boundary; and,

wherein the pulsed energization is applied across said first and second terminals, the pulsed energization being adaptively tuned in amplitude to define separately adjusted peak amplitudes in opposing directions relative to a predetermined baseline amplitude for raising and lowering the temperature of said MPT portion, said MPT portion at the predetermined baseline amplitude being biased to the intermediate phase, whereby the peak amplitudes may be different in the opposing directions depending on the predetermined baseline amplitude.

10 . The device as recited in claim 9 , wherein said MPT portion includes an FeRh material; and, the critical temperature for traversal is greater at each of the first and second phase boundaries for a rising direction of temperature change towards the FM phase than for a lowering direction of temperature change towards the AFM phase.

11 . The device as recited in claim 10 , wherein the pulsed energization includes resistive heating by applying a pulsed voltage signal between said first and second terminals coupled to said MPT portion.

12 . The device as recited in claim 10 , wherein said MPT portion is selectively tunable in phase transitioning response based on at least one of a plurality of predetermined tuning parameters including substitutional doping, material strain, and geometric patterning.

13 . The device as recited in claim 9 , wherein said MPT portion is configured to retain the electrical conduction path in one of the ON and OFF states when stabilized in temperature to remain magnetically within the intermediate phase, said MPT portion settling to a temperature within the intermediate phase responsive to either a substantially constant direct current bias of predetermined voltage or a pulsed bias of a predetermined baseline voltage applied thereacross.

14 . A method for high speed metamagnetic resistive switching between predetermined ON and OFF states for memory, comprising:

establishing a substrate;

establishing first and second terminals on said substrate;

forming at least one metamagnetic phase transitioning (MPT) portion on said substrate, said MPT portion being coupled to said first and second terminals to define an electrical conduction path in resistivity adjustable manner therebetween;

selectively tuning said MPT portion for temperature-responsive bidirectional transitions in phase between antiferromagnetic (AFM) and ferromagnetic (FM) phases through an intermediate phase, said selective tuning includes:

defining first and second phase boundaries between the intermediate phase and the AFM and FM phases respectively; and,

defining for each of the first and second phase boundaries different critical temperatures for traversal depending on direction of traversal, the different critical temperatures for each of the first and second phase boundaries being mutually offset by a hysteretic shift;

boosting said MPT portion in magnetic phase across the first phase boundary responsive to thermal actuation pulsed in a first direction to reach or exceed both the critical temperatures of the first phase boundary in the first direction; and,

boosting said MPT portion in magnetic phase across the second phase boundary responsive to thermal actuation pulsed in a second direction to reach or exceed both the critical temperatures of the second phase boundary in the second direction;

wherein the pulsed thermal actuation includes pulsed energization applied across said first and second terminals, the pulsed energization being adaptively tuned in amplitude to define separately adjusted peak amplitudes in the first and second directions relative to a predetermined baseline amplitude, said MPT portion at the predetermined baseline amplitude being biased to the intermediate phase, whereby the peak amplitudes may be different in the first and second directions depending on the predetermined baseline amplitude;

the electrical conduction path of said MPT portion being thereby adjusted in resistivity for switching between the ON and OFF states.

15 . The method as recited in claim 14 , wherein:

the pulsed thermal actuation for selectively switching said MPT portion from the OFF state to the ON state includes raising said MPT portion in temperature up to at least the higher of the critical temperatures for the second boundary; and,

the pulsed thermal actuation for selectively switching said MPT portion from the ON state to the OFF state includes lowering said MPT portion in temperature down to at least the lower of the critical temperatures for the first boundary.

16 . The method as recited in claim 14 , wherein said MPT portion varies in resistivity through the intermediate phase in substantially linear response to variation in temperature, said MPT portion being characterized at each temperature within the intermediate phase by different resistivity values mutually offset by a hysteretic shift depending on which of the AFM and FM phases said MPT portion last transitioned into the intermediate phase from.

17 . The method as recited in claim 14 , wherein said MPT portion is formed substantially of a metallic material.

18 . The method as recited in claim 17 , wherein the metallic material of said MPT portion is formed to include an FeRh material; and, said pulsed energization includes resistive heating by applying a pulsed voltage signal between said first and second terminals coupled to said MPT portion.

19 . The method as recited in claim 14 , wherein said MPT portion is stabilized in temperature to remain magnetically within the intermediate phase for retaining the electrical conduction path in one of the ON or OFF state, said MPT portion settling to a temperature within the intermediate phase responsive to either a substantially constant direct current bias of predetermined voltage or a pulsed bias of a predetermined baseline voltage applied thereacross.

20 . The method as recited in claim 14 , wherein said MPT portion is selectively tuned in phase transitioning response based on at least one of a plurality of predetermined tuning parameters including substitutional doping, material strain, and geometric patterning.