PROBLEM TO BE SOLVED: To provide a gradiometer with which it is possible to detect a minute magnetic field induced by magnetic particulates, etc., with high accuracy, suppressing the effect of an excited magnetic field from the outside or terrestrial magnetism.SOLUTION: A magnetic field sensor comprises: a first sensor head 12 consisting of a first magnetic core 10 and a first detection coil 11 wound around the first magnetic core 10 a second sensor head 22 consisting of a second magnetic core 20 and a second detection coil 21 wound around the second magnetic core 20 and connected in anti-series to the first detection coil 11 an excitation coil for applying an excitation magnetic field to a magnetic particulate aggregate that is an object of detection and magnetic flux adjustment means for changing the relative positions of the first sensor head 12 and/or the second sensor head 22 and the excitation coil and thereby increasing or reducing one of an interlinkage flux that affects the first sensor head and an interlinkage flux by which the excitation magnetic field affects the second sensor head as compared with the other.SELECTED DRAWING: Figure 1COPYRIGHT: (C)2018,JPO&INPIT【課題】磁気微粒子等が誘発する微小な磁界を、外部からの励磁された磁界や地磁気の影響を抑えて高感度に検出することができるグラディオメータを提供する。【解決手段】第1の磁気コア10及び当該第1の磁気コア10に巻回される第1の検出コイル11からなる第1のセンサヘッド12と、第2の磁気コア20及び当該第2の磁気コア20に巻回され、前記第1の検出コイル11と逆直列に接続される第2の検出コイル21からなる第2のセンサヘッド22と、検出対象である磁気微粒子集合体に対して励磁磁界を印加する励磁コイルと、前記第1のセンサヘッド12又は前記第2のセンサヘッド22の少なくとも一方と前記励磁コイルとの相対位置を変化させて、前記第1のセンサヘッドに影響する鎖交磁束又は前記励磁磁界が前記第2のセンサヘッドに影響する鎖交磁束の一方を他方に比べて増加又は減少させる磁束調整手段とを備える【選択図】図1
