. The Bell System technical journal . olumn of figures contains values of/max. obtained near room-temperature; the second, values measuredat the temperature of boiling hydrogen, inserted here for futurereference.* * These values may be described as the saturation magnetization of a cubiccentimetre of the materials in question. Dividing each by the density p of thematerial, we obtain the saturation magnetization per gramme. Multiplying thisby A, the atomic weight of the element or molecular weight of the compound (if thematerial is of either sort) we get the saturation magnetization per gramme-
. The Bell System technical journal . olumn of figures contains values of/max. obtained near room-temperature; the second, values measuredat the temperature of boiling hydrogen, inserted here for futurereference.* * These values may be described as the saturation magnetization of a cubiccentimetre of the materials in question. Dividing each by the density p of thematerial, we obtain the saturation magnetization per gramme. Multiplying thisby A, the atomic weight of the element or molecular weight of the compound (if thematerial is of either sort) we get the saturation magnetization per gramme-mole-cule. This last is the quantity most often tabulated, being sometimes expressed inmagnetons (units equal to 1126 C. G. S. units; cf. page 353). It may be advisableto recall that an isolated cube containing one cubic centimetre, or one gramme, orone gramme-molecule of material would not acquire the magnetization in questionat any finite field, since it could not be magnetized uniformly. I CONTEMPORARY ADVANCES IN PHYSICSTABLE 319. ■max. (20° K.) Iron Nickel Cobalt Alloy FeiCo Permalloy Ni per cent, Fe per cent Heusler alloy Cu 75 per cent, Mn 14 per cent, Al 10 per cent Magnetite Pyrrhotine 1742505 518 The dependence of the initial curve upon temperature and strainis great and important; but it is expedient to reserve discussion ofthese variations to later sections. The Hysteresis-Loops Any ferromagnetic material has an infinite variety of hysteresis-loops, almost any one of which may turn up in practice; but I willlimit this discussion to those obtained by a particular procedure, thus:Commence by demagnetizing the sample—increase H gradually toany desired value, denote this by iJo—decrease H gradually to andthrough zero, reversing it and bringing it to the equal and oppositely-directed value (— Ho)—return gradually to + i7o—return to (— H^)—and so over and over again, ten or twenty times at the least. Thepoint representing / as function of H, or
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