Focused Practice

I. Answer the following questions:

1. What are perturbations of the magnetic flux in iron and steel due to?

2. What was the chance discovery of Hoke?

3. Who discovered the technique of magnetic particle inspection?

4. When was it discovered?

5. What did DeForest’s work involve?

6. What is the need to use magnetic powders with uniform properties?

II. Analyse the grammar structures underlined in the above text.

III. Speak on: The subject of flaw detection.

Unit 12 Grammar: Simple, Progressive and Perfect Tenses. The Infinitive Word List:

1. magnetoresistive materials	магниторезистивные материалы
2. magnetic recording heads	записывающие магнитные головки
3. disk drive	дисковый накопитель
4. storage requirements for applications	требования к объему сохранения данных для различных применений
5. giant magnetoresistive materials	материалы с очень большим магнитным сопротивлением
6. tunneling device	прибор, работающий на основе туннельного эффекта
7. fringing fields	краевые поля
8. write pole	записывающий полюс
9. write coils	записывающие катушки
10. read width	ширина считывания

Impact of New Magnetoresistive Materials on Magnetic Recording Heads

Magnetoresistive recording heads have only recently been introduced into the magnetic recording industry but they have heralded a new interest in the basic properties of magnetic materials. What is driving this interest is the direct link between the magnitude of the magnetoresistance of the sensor material and the final storage capacity of the disk drive. With the storage requirements for applications increasing rapidly it is not surprising that there has been a keen interest in pushing materials to larger magnetoresistance. New multilayer films, for example the giant magnetoresistive materials, are being developed with a variety of properties that can be tailored to meet the needs of the new technology. Other novel sensors have been proposed, for instance tunneling devices which depend on the tunneling of electrons from one magnetic layer to another, and colossal magnetoresistive materials which have a structure similar to high Ts superconductors. With the phenomenon of electron transport at small length scales becoming better understood it is well within possibility that a “magnetic switch” is only just around the corner.

In an example of a typical magnetoresistive (MR) head geometry that could be used to achieve 16 Mb/mm² sandwiched between shields is a magnetoresistive element with two conductors that make contact with the MR element. A sense current is used to measure the change in resistance of the element as a recorded bit in the media passes underneath the head. The bits are written by fringing fields that jump the gap between the write pole and the shield when current is applied to the write coils.

The read width in this particular head geometry is defined by the region of the element that is sensed by the two contacts. The distance between the shields controls the resolution of the sensor along the track. The distance from the bottom of the sensor to the top of the magnetic layer in the media is defined as the magnetic spacing.