Here, however, we are interested in a much more robust, essentially classical effect, that occurs at higher temperatures and does not require the presence of disorder: the spin Coulomb drag, ,. Electron–electron interactions in combination with impurity scattering lead to many fascinating effects, which usually appear at temperatures lower than the inverse of the electron-impurity scattering time. To keep our discussion as simple as possible we assume that both the ferromagnets and the semiconductor are ordinary diffusive conductors and that the electron–electron interaction plays a significant role only in the semiconductor, due to its lower electronic density. In this paper we wish to explore a special aspect of the problem, which is particularly close to the area to which Professor Quinn has made so many outstanding contributions, namely the role played by the Coulomb interaction between the electrons. Needless to say, both the magnetoresistance and the spin-current injection efficiency β=( j ↑ −j ↓ )/Jp of the FM/NM/FM device have been theoretically studied by many workers in a great many different situations. Another interesting property of this circuit is that in case (a) the current J injected in the semiconductor may exhibit a significant degree of spin-polarization, namely, the ratio ( j ↑− j ↓)/ J in the semiconductor may be close to the polarization p of the ferromagnetic electrodes: this is an instance of electrical spin-current injection, ,, and is believed to be a most promising avenue towards a practical use of spins in electronics. This magnetoresistance effect, ,, has already found several applications in metal-based devices. Two ferromagnetic (FM) electrodes (metals or semiconductors) are separated by a nonmagnetic (NM) semiconductor layer: the resistance of the structure is found to depend on the relative orientation of the magnetizations in the FM layers, going from ‘low’ in the parallel configuration (a) to ‘high’ in the antiparallel configuration (b). Potential energy is equal to $mgh'$(which is less than the kinetic energy you provided atfirst).Ī part of the kinetic energy surely has gone somewhere?Īns is yes,when you stop the object with your hand ,a part is converted into sound and and a part to heat.One of the central problems of semiconductor spintronics, is the description of the current characteristics of the 3-layer structure shown in Fig. Now what happen when you stop the object at a height $h'$? Its potential energy will be equal to $1/2 mv^2$.(That means the whole kinetic energy is converted into potential energy). If you dont stop the object with your hand(or anyhow) it will go to a height $h$,and at height $h$ Now if you throw an object with kinetic energy $1/2 mv^2$(i will assume now that there is no air) When you throw the object upward the speed of object keep decreasing that means the kinetic energy also keep decreasing.īut potential energy of the object keep also increasing. When a body go upwards against gravity its kinetic energy changes to potential energy and at maximum height the whole kinetic energy is converted into potential energy.īut if air is present the kinetic energy also converted into heat and sound so the potential energy at the maximum height is less than the initial kinetic energy of the object.ĮDIT:Potential energy only depend on the final position.It doesnt matter how the object reach the height $h'$ ,potential energy is still $mgh'$. Kinetic energy is converted into sound,heat,potential energy etc etc. what can be those energies and on which cases these will happen respectively ?

Now kinetic energy will transform into some other energy.

Assume an object is moving and it is stopped at a point.

Sto potential energy entangler