NANOMAGIQC

Project Revision

Workpackage 1 Revised (cont.)

Description of the work (cont.)

A very promising approach towards the quantum limited detection of molecular clusters magnetic moments has been recently explored both at NIST and at IBM-Almaden using nano-mechanical resonator devices in combination withferromagnetic resonance detection techniques.

In particular, H. J. Mamin and D. Rugar (Applied Physics Letters 79 (2001) 3358) at IBM, have demonstrated force sensitivities of 8.2×10^-19 N/Hz^1/2 (sub-attonewton range) at 110 mK, in a development towards single electronic spin detection by magnetic resonance force microscopy (MRFM).

Using similar MRFM techniques, J.Moreland at NIST (Journal of Physics D: Applied Physics 36 (2003) R39) theoretically predicts that it is feasible to measure magnetic moments as small as 10^-23 A·m² (1 mB) if adequate microcantilever based devices can be developed for low temperature operation. His current experimental sensitivity at room temperature is of the order of 10^-11 A·m² but many orders of magnitude improvement is expected in the mK range.

M. L. Roukes group at Caltech is presently pursuing a similar development of quantum limited nanomechanical devices in connection with people in the Institute for Quantum Information (John Preskill et al.). The final goal is, again, single electron spin detection.

The group at CSIC-IMM has sufficient experience with the selective etching and nanolithography of MBE grown GaAs nanostructures to be able to fabricate, along the 2nd year of the project, nanomechanical devices with state-of-the-art technology and performances, similar to those developed by the group of M. L. Roukes (Applied Physics Letters 81 (2002) 2253).

Ferromagnetic resonance measurements on single magnetic clusters are envisaged by cooling down CSIC-IMM devices in the dilution refrigerator system of the UB group. Instead of the more conventional optical detection scheme used by main US groups, a novel and original detection scheme based on the modulation of tunnelling current through a microfabricated nanogap in GaAsP/AlGaAs heterostructures will be explored.

This scheme is, in principle, the most adequate for measurements in the mK temperature range and it can be scalable to a multi-qubit scheme. The collaboration with the UB group, with experience on FMR measurements at low temperatures, will be highly instrumental in order to design and carry out the experiments and to interpret results.

Mn₁₂ molecular clusters positioning on the devices is obviously still a difficult task. Various options, including PLD (Pulsed Laser Deposition) and AFM techniques, will be pursued in collaboration with the CSIC-ICMAB group, in order to establish a reliable and scalable procedure that will be also explored in parallel for the micro-SQUID approach.

Deliverables

• D1.1 (months 18, 24). Report on the applicability of micro-SQUID and micro-Hall probes to the measurement of the properties of nanomagnets. Other measurement methods (e.g. magneto-optical measurements), should they emerge, will also be investigated and reported upon.
• D1.2 (month 24, month 36). Report on measurement devices and methods to measure the properties of small clusters of nanomagnets having total spin of 10000 or less and the suitability of such methods to the measurement of single magnetic qubits.

Milestones

• M1.3 (month 18). Measurements on candidate devices to show theirsensitivity and suitability as devices for the measurement of single nanomagnets.
• M1.4 (month 36). Measurements on nanomagnets, using state-of-the-art devices and methods, including time resolved measurements and measurements on small clusters of nanomagnets.

 

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