Stressed magnetoresistive tamper detection devices

• US 8,294,577 B2
• Filed: 03/10/2008
• Issued: 10/23/2012
• Est. Priority Date: 03/09/2007
• Status: Active Grant

• Current Assignee: NVE Corporation
• Original Assignee: NVE Corporation
• Inventors: Deak, James G.
• Primary Examiner(s): Zimmerman, Brian
• Assistant Examiner(s): Alizada, Omeed
• Application Number:
  US12/075,148
• Publication Number:
  US 20080247098A1
• Time in Patent Office: 1,688 Days
• Field of Search: 340/568.1, 340/540, 340/657, 324/110, 360/328
• US Class Current: 340/568.1
• CPC Class Codes: G11C 11/16 using elements in which the storage effect is based on magnetic spin effect
• CPC Class Codes: G11C 11/161 details concerning the memory cell structure, e.g. the layers of the ferromagnetic memory cell
• CPC Class Codes: G11C 11/1675 Writing or programming circuits or methods
• CPC Class Codes: G11C 11/1695 Protection circuits or methods

Abstract

A tamper sensing system mounted with respect to a protected structure so as to have corresponding stress changes occur therein in response to selected kinds of tamperings with said protected structure comprising a first pair of stress affected magnetoresistive memory devices each capable of having a magnetic material layer therein established in a selected one of a pair of alternative magnetization states if in a first kind of stress condition and of being established in a single magnetization state if in an alternative second kind of stress condition, and the magnetic material layer in each having a magnetization in a first direction in one of the pair of alternative magnetization states and in a second direction in that remaining one of the pair of magnetization states. A first magnetizing electrical conductor extends adjacent to each of the first pair of stress affected magnetoresistive memory devices to establish said magnetic material layer in that one of said pair of alternative magnetization states thereof so as to have its said corresponding magnetization be oppositely directed with respect to said magnetization of that other. The first pair of stress affected magnetoresistive memory devices can each be provided by a spin dependent tunneling device having differing numbers of magnetization states available thereto depending on whether being in differing ones of alternative stress conditions.

Claims

1. A tamper sensing system mounted with respect to a protected structure so as to have corresponding stress changes occur therein in response to selected kinds of tamperings with said protected structure, said system comprising:

a first pair of stress affected magnetoresistive memory devices each capable of having a magnetic material layer therein established in a selected one of a pair of alternative magnetization states if in a first kind of stress condition and of being established in a remaining magnetization state if in an alternative second kind of stress condition and with said magnetic material layer in each having a magnetization in a first direction in one of said pair of alternative magnetization states and in a second direction in that remaining one of said pair of magnetization states, said first pair of stress affected magnetoresistive memory devices being mounted together such that at least one of said first and second directions thereof at least in part parallels an aligning direction that parallels at least in part at least one of said first and second directions of that other one remaining; and

a first magnetizing electrical conductor extending adjacent to each of said first pair of stress affected magnetoresistive memory devices such that providing an electrical current therethrough to generate a corresponding magnetic field thereabout establishes said magnetic material layer of each of said first pair of stress affected magnetoresistive memory devices in that one of said pair of alternative magnetization states thereof so as to have said magnetization corresponding thereto be oppositely directed with respect to said magnetization of that other magnetic material layer insofar as components thereof substantially parallel to said aligning direction when each of said first pair of stress affected magnetoresistive memory devices is provided with a first kind of stress condition.

2. The system of claim 1 further comprising a pair of electrodes on opposite ends of each of said first pair of stress affected magnetoresistive memory devices with said first pair of stress affected magnetoresistive memory devices electrically connected in series to one another at an electrode of each and at a remaining electrode of one to a series devices electrical resistance determiner.

3. The system of claim 1 further comprising a pair of electrodes on opposite ends of each of said first pair of stress affected magnetoresistive memory devices with said first pair of stress affected magnetoresistive memory devices each electrically connected to one another at an electrode of each and at a remaining electrode of each to a device electrical resistance determiner.

4. The system of claim 1 further comprising each of said first pair of stress affected magnetoresistive memory devices being provided by a spin dependent tunneling device having differing numbers of magnetization states available thereto depending on whether being in differing ones of alternative stress conditions, said spin dependent tunneling device comprising:

an electrically insulative material intermediate layer, said intermediate layer having two major surfaces on opposite sides thereof;

a magnetization reference layer on one of said intermediate layer major surfaces, said magnetization reference layer having a relatively fixed direction of magnetization; and

a memory film of an a magnetostrictive, anisotropic ferromagnetic material on that remaining one of said intermediate layer major surfaces having a magnetization directed at an angle with respect to said relatively fixed direction due to an effective magnetic bias field being present to result in said device having an electrical resistance versus applied external magnetic field characteristic in a first kind of stress conditions with unequal coercivities for external magnetic fields applied in opposite directions, said magnetostrictive, anisotropic ferromagnetic material being such that said device in one kind of stress conditions has a coercivity with a magnitude exceeding that of said effective magnetic bias field and in another kind of stress conditions has a coercivity with a magnitude less than that of said effective magnetic bias field.

5. The system of claim 1 further comprising:

a second pair of stress affected magnetoresistive memory devices each capable of having a magnetic material layer therein established in a selected one of a pair of alternative magnetization states if in a first kind of stress condition and of being established in a remaining magnetization state if in an alternative second kind of stress condition and with said magnetic material layer in each having a magnetization in a first direction in one of said pair of alternative magnetization states and in a second direction in that remaining one of said pair of magnetization states, said second pair of stress affected magnetoresistive memory devices being mounted together such that at least one of said first and second directions thereof at least in part parallels an aligning direction that parallels at least in part at least one of said first and second directions of that other one remaining; and

a second magnetizing electrical conductor extending adjacent to each of said first pair of stress affected magnetoresistive memory devices such that providing an electrical current therethrough to generate a corresponding magnetic field thereabout establishes said magnetic material layer of each of said second pair of stress affected magnetoresistive memory devices, provided with a first kind of stress condition, in that one of said pair of alternative magnetization states thereof so as to have its said corresponding magnetization be oppositely directed with respect to said magnetization of that other insofar as components thereof substantially parallel to said aligning direction.

6. The system of claim 5 further comprising a pair of electrodes on opposite ends of each of said first pair of stress affected magnetoresistive memory devices and a pair of electrodes on opposite ends of each of said second pair of stress affected magnetoresistive memory devices with said first pair of stress affected magnetoresistive memory devices electrically connected together at a junction to be further electrically connected in series between first and second termination regions suited for electrical connection to a source of electrical energization and with said second pair of stress affected magnetoresistive memory devices electrically connected together at a junction to be further electrically connected in series between said first and second termination regions, there further being a voltage difference sensor electrically connected between said junctions.

7. The system of claim 1 further comprising said first magnetizing electrical conductor having therein a fusing arrangement such that providing an electrical current therethrough to generate a corresponding magnetic field about said first pair of stress affected magnetoresistive memory devices to establish in said magnetic material layer of each one of said pair of alternative magnetization states thereof causes said fusing arrangement to subsequently to interrupt said electrical current and prevent reestablishing thereafter further electrical current in said first magnetizing electrical conductor.

8. The system of claim 1 wherein said magnetic material layer in said first pair of stress affected magnetoresistive memory devices is of a magnetostrictive material and positioned in a bias magnetic field.

9. The system of claim 1 further comprising said first pair of stress affected magnetoresistive memory devices being positioned in a housing with a housing structure portion forced thereagainst sufficiently to establish each in said first kind of stress condition.

10. The system of claim 9 wherein reducing said housing structure portion force against said first pair of stress affected magnetoresistive memory devices sufficiently establishes them in said second kind of stress condition.

11. The system of claim 10 further comprising said housing having an electronic information storage system having information stored therein that is positioned in said housing electrically coupled to said first pair of stress affected magnetoresistive memory devices such that said first pair of stress affected magnetoresistive memory devices being changed from said first kind of stress condition to said second kind of stress condition results in a change in said information stored in said electronic information storage system.

12. The system of claim 3 further comprising said first pair of stress affected magnetoresistive memory devices having said electrodes where electrically connected to one another being together electrically connected to a first termination region suited for electrical connection to a source of electrical energization and said first pair of stress affected magnetoresistive memory devices each being further electrically connected through a corresponding device selection transistor to said device electrical resistance determiner which is electrically connected to a second termination regions suited for electrical connection to said source of electrical energization.

13. The system of claim 12 wherein said first magnetizing electrical conductor is electrically connected in series with a corresponding magnetization selection transistor between first and second termination regions suited for electrical connection to a source of electrical energization.

14. The system of claim 4 wherein said magnetization reference layer of one of said first pair of stress affected magnetoresistive memory spin dependent tunneling devices is electrically connected to said memory film of that remaining one of one of said first pair of stress affected magnetoresistive memory spin dependent tunneling devices with a selected one of that remaining said magnetization reference layer and said memory film being electrically connected to a series devices electrical resistance determiner.

15. The system of claim 4 wherein said magnetization reference layers of said first pair of stress affected magnetoresistive memory spin dependent tunneling devices form a reference layer pair and said memory films of said first pair of stress affected magnetoresistive memory spin dependent tunneling devices form a memory layer pair and further comprising a selected one of said reference and memory layer pairs being electrically connected to a first termination region suited for electrical connection to a source of electrical energization and that remaining pair being electrically connected through a corresponding device selection transistor to a device electrical resistance determiner which is electrically connected to a second termination regions suited for electrical connection to said source of electrical energization.

16. The system of claim 15 wherein said first magnetizing electrical conductor is electrically connected in series with a corresponding magnetization selection transistor between first and second termination regions suited for electrical connection to a source of electrical energization.

17. The system of claim 5 further comprising one of said first pair of stress affected magnetoresistive memory devices and one of said second pair of stress affected magnetoresistive memory devices being electrically connected together at a junction as a first series pair with electrodes on opposite ends thereof to have said first series pair electrically connected in series between first and second termination regions suited for electrical connection to a source of electrical energization with said first series pair of memory devices each having said first direction thereof being a common direction, and with that remaining one of said first pair of stress affected magnetoresistive memory devices and that remaining one of said second pair of stress affected magnetoresistive memory devices being electrically connected together at a junction as a second series pair with electrodes on opposite ends thereof to have said second series pair electrically connected in series between said first and second termination regions with said second series pair of memory devices each having said first direction thereof being a common direction.

18. The system of claim 5 further comprising one of said first pair of stress affected magnetoresistive memory devices and one of said second pair of stress affected magnetoresistive memory devices being electrically connected together at a junction as a first series pair with a termination electrode and a sense junction electrode on opposite ends thereof to have said first series pair termination electrode electrically connected to a first termination region suited for electrical connection to a source of electrical energization with said first series pair of memory devices each having said first direction thereof being a common direction, and with that remaining one of said first pair of stress affected magnetoresistive memory devices and that remaining one of said second pair of stress affected magnetoresistive memory devices being electrically connected together at a junction as a second series pair with a sense junction electrode and a termination electrode on opposite ends thereof to have said second series pair termination electrode electrically connected to said second termination regions with said second series pair of memory devices each having said first direction thereof being a common direction, said first and second series pairs sense electrodes being electrically connected to one another.

19. The system of claim 5 further comprising a pair of electrodes on opposite ends of each of said first pair of stress affected magnetoresistive memory devices which are electrically connected to one another at an electrode of each and electrically connected to a first termination region suited for electrical connection to a source of electrical energization with said first pair of stress affected magnetoresistive memory devices each being further electrically connected through a corresponding device selection transistor to a device electrical resistance determiner which is electrically connected to a second termination regions suited for electrical connection to said source of electrical energization, and a pair of electrodes on opposite ends of each of said second pair of stress affected magnetoresistive memory devices which are electrically connected to one another at an electrode of each and electrically connected to said first termination region suited for electrical connection to a source of electrical energization with said second pair of stress affected magnetoresistive memory devices each being further electrically connected through a corresponding device selection transistor to said device electrical resistance determiner which is electrically connected to a second termination regions suited for electrical connection to said source of electrical energization, said first and second pairs of stress affected magnetoresistive memory devices being positioned in a housing with a housing structure portion forced thereagainst sufficiently to establish each in said first kind of stress condition such that reducing said housing structure portion force against said first and second pairs of stress affected magnetoresistive memory devices sufficiently establishes them in said second kind of stress condition, said housing having an electronic information storage system having information stored therein that is positioned in said housing electrically coupled to said first and second pairs of stress affected magnetoresistive memory devices so that coding key information stored in said first and second pairs of stress affected magnetoresistive memory devices must be used by said electronic information storage system to obtain information stored therein such that said first and second pairs of stress affected magnetoresistive memory devices being changed from said first kind of stress condition to said second kind of stress condition results in a change in said coding key information stored therein.