The present invention relates, in general terms, to magnetoresistance sensors and methods of fabrication thereof. The magnetoresistance sensor comprises a continuous graphene layer disposed on a corrugated and/or stepped surface of a substrate. At least two conductive elements are in contact with the graphene layer. The graphene layer substantially conforms to the corrugated and/or stepped surface of the substrate.

A method of increasing coercivity of an Nd—Fe—B sintered permanent magnet includes a step of providing an organic film. A powder, containing at least one heavy rare earth elements, is uniformly deposited on the organic film forming a diffusion source. Then, a sintered Nd—Fe—B magnet block having a pair of block surfaces extending perpendicular to a magnetization direction is provided. Next, the diffusion source is deposited on at least one of the block surfaces with the powder being in abutment relationship with at least one of the block surfaces. After depositing the diffusion source, the sintered Nd—Fe—B magnet block containing the diffusion source is pressed allowing the powder of the diffusion source to be in close contact with the block surface. The diffusion source is then diffused into the sintered Nd—Fe—B magnet block to produce a diffused magnet block. Next, the diffused magnet block is aged.

A graphene structure is provided. The graphene structure comprises a substrate layer and at least two graphene layers disposed on the substrate. The at least two graphene layers comprises a gate voltage tuned layer and an effective graphene layer and the effective graphene layer comprises one or more graphene layers. A magnetoresistance ratio of the graphene structure is determined by a difference in a charge mobility and/or a carrier density between the gate voltage tuned layer and the effective graphene layer. The charge mobility and/or the carrier density of the gate no voltage tuned layer is tunable by a gate voltage applied to the graphene structure. A magnetic field sensor comprising the graphene structure is also provided.

A method of increasing coercivity of an NdFeB sintered permanent magnet includes a step of providing an organic film. A powder, containing at least one heavy rare earth elements, is uniformly deposited on the organic film forming a diffusion source. Then, a sintered NdFeB magnet block having a pair of block surfaces extending perpendicular to a magnetization direction is provided. Next, the diffusion source is deposited on at least one of the block surfaces with the powder being in abutment relationship with at least one of the block surfaces. After depositing the diffusion source, the sintered NdFeB magnet block containing the diffusion source is pressed allowing the powder of the diffusion source to be in close contact with the block surface. The diffusion source is then diffused into the sintered NdFeB magnet block to produce a diffused magnet block. Next, the diffused magnet block is aged.

Systems and methods are provided for fabricating an assembly with a controllable magnetic state and ferromagnetic resonance. A layer of twisted bilayer graphene is positioned in contact with a transition metal dichalcogenide to form a structure with an interface between the twisted bilayer graphene and the transition metal dichalcogenide. Energy is applied to the interface to adjust one of a magnetic state associated with the interface and a ferromagnetic resonance associated with the interface.