The Magnetostriction and Resistance of Iron and Nickel

C. W. Heaps
1915 Physical Review  
T HE experiments described in this paper were undertaken with the object of making simultaneous measurements of magnetostriction and resistance in the same specimens of iron and of nickel. The importance of making different experiments on the same specimen is very evident when a comparative study is to be made. The galvanomagnetic properties of a metal are so intimately connected with the other properties such as purity, hardness, crystalline structure, etc., that results of different
more » ... ors using different samples cannot be compared with each other with any degree of exactness. The magnetostriction of iron and nickel has been rather extensively studied by different experimenters, and in a general way all results indicate that a bar of iron has its length increased parallel to the direction of a weak magnetic field and decreased when the field is strong. A bar of nickel suffers a decrease in length for all fields. Different samples of these metals, however, behave differently. Bidwell 1 states that he has obtained in one specimen of iron a contraction for all field strengths and S. R. Williams 2 has observed an initial lengthening in the case of nickel. Whether these diversified results are due to differences in the character of the specimen itself or to differences in the uniformity of the magnetic field applied, one can easily see the necessity of making comparative studies from the same sample under the same conditions. The importance of considering magnetostriction in connection with resistance is made evident by the failure of theory to explain the effect of magnetization upon resistance without bringing into consideration some term depending on the configuration of the molecules in the metal. A magnetic field may cause the free electrons constituting the current to change their paths and hence the resistance is altered. Also, the magnetic field produces a change in the molecular configuration which further affects the resistance. Magnetostriction must also be associated with a change in molecular arrangement, so that by studying magneto-1
doi:10.1103/physrev.6.34 fatcat:ee67nwzyfzcvzbwjfo6yq5n4gy