Instrument S.A.

PDI 5025 MAGNETIC HYSTERESIS CYCLE MEASUREMENT

METROLAB 1 10, Chemin du pont-du-centenaire ch- 1228 GENEVA / SWITZERLAND Fox:41(22)794 1 1 20 Tel: 41 (22)794 l l 2 1

METROLAB instruments SA

Metrolab/Geneva, May 1991

The PDI 5025 can be used as the basic component of an hysteresis curve determination system. We have measured the hysteresis cycle of three different samples.

The experiment configuration is shown in fig. 1; figures 2 to 9 show the result of the measurement. In our configuration, the channel "AI1 of the PDI 5025 measures the voltage across the reference resistor which is proportional to the - current and therefore to the applied magnetic field strength H. Channel lIB1l measures the magnetic flux changes (6+) within the sample. The magnetic field B is proportional to the flux plus the initial value B By plotting results of channel llBtlvs channel "AI1, we obtain t%e hysteresis cycle. The shape of the ramped field cycle (applied magnetic field H) is shown in fig. 2. It starts at point (a) and ends at point (b) lasting 30 seconds. The PDI is programmed in order to get data before and after the field cycle to determine the voltage offset and integrator drift respectively for channel I1Al1 and I1Bl1. The offset and drift for both channels are considered for each measurement. The PDI cycle lasts 50 seconds and triggers are generated every 100 ms (TRI,,0/500,100) .

An example of the magnetic field measured within the samplefS material is shown in fig. 3. Prior to the measurement, the material is demagnetized and the final level represents the sample remanence. Three different samples with different characteristics have been measured. - sample #l : material type P2 with a permeability of about 200000. - sample #2 : material type P6 with a permeability greater than sample #l one.

- sample #3 : material type PC with a permeability smaller than sample #l one.

Figures 4 to 9 show the hysteresis cycles and several enlarged regions of it. All data are corrected for the offset/drift effect.

110, ch. du Pont-du-Centenaire Telephone 41 (22) 794 11 21 Bank, Credit Suisse Geneve CH-1228 Geneva/Plan-les-Ouates Telefax 41 (22) 794 11 20 No. 443 820-51 Switzerland mowInstruments SA

The PDI 5025 data acquisition sequence

The PDI 5025 is programmed to generate triggers in time:

where :

Each channel integrates its input voltage during the periods delimited by two consecutive triggers [ti,l = ti-6t ; ti]:

The channel ItAttis used as a voltmeter. Indicating by Vi the voltage at time ti:

vi = A + a+i+l A) /2. at [volts] The voltage measured in this way represents an average value during the time period [ti-6t ; ti+6t].

The channel "Bt1 is used as an integrator measuring the magnetic field at time Bi: i (N-A)-Bi + (N-A)BO [Tesla]

j=1 2 where : B. = field at t=O and N-A= coil surface (m ) HROmInstruments SA

Experiment configuration layout

Programmable Ramp Generator Driven Power Generator

PDI 5025

W20 turns / ~ostComputer - PDI 5025 channel "Au : Hi (used as voltmeter) - PDI 502-5 channel "Bn : Bi

- Channel "A" measures the voltage across the reference resistor which is proportional to the applied magnetic field strength H. - Channel "B" measures the difference of magnetic flux within the material from the starting point.

Fig. 3. METROW Instruments SA

---- 38 sec --- U Cuoltsl I -I

time kecl

Fig. 2

Voltage across the reference resistor : the P1 and P2 plateaus are used to determine the channel input offset.

B 118-4 U.sl 38 sec I

-1 ' 8 S 10 15 20 25 38 35 40 45 Csec l I Fig. 3

Example of magnetic field within a sample: the P1 and P2 plateaus are used to determine the drift of the channel. f l-ubc dat : material . Sample l1 P2 corrected

T -. =-88.9719 XIlftX= 89.453 Xscale= 17.84249 [mVl = -3194 = 3321 Yscale = 651 .5 CM-8 U.sl

Fig. 4 Hysteresis cycle for sample #l. The material does not reach the full saturation.

a1~=-m.g71gI mfiX= 89.453 Xscale= 17.04249 CmVl (~IH= -3194 YHAX = 3321 Yscale = 651.5 [M-8 U.sl

Fig. 5

et ail of the cycle of Fig. 4 showing the initial magnetization. .. - METROLAB Instruments SA

f 2-ubc . dat Sample U1 : maerial P2 corrected

U (or H)

1 xn IN = -447, ion = 446 .B778 Xscale = 89.4065 1d l WIN = -2510 YflAX = 9719 Yscale = 1222.9 118-8 U.sl Fig. 6

Hysteresis cycle for sample #l. The cycle starts from a non zero magnetized state. Sample 112 : material P6 f 3-ubc .dat correctd

U (or H)

= 448.3993 Xscale = 89.50799 [&l ?!In = -13145 YnAX = 2666 Yscale = 1581.l 118-8 U.SI Fig. 7

Hysteresis cycle for sample #2. The cycle starts from a non zero magnetized state. MOWInstruments SA

f 3-ubc .dat Sample U2 : material P2 corrected

= -18 XMX = 448.3993 Xscale = 45.83993 [NI = -688 YNAX = 2666 Yscale = 326 -6 1x4-8 U.sl I I t Fig. 8 Detail of the cycle of Fig. 7 showing the effect of the inversion of the scan trajectory. Sample U3 : material PC f 4-ubc .dat corrected

l HIN = -448 .2896 MAX = 447.4553 Xscale = 89.56649 [NI HIN = -7046 YflAX = 7818 Yscale = 1405.6 CB-B U.rl

Fig. 9

Hysteresis cycle for sample #3.