Statistical and Low Temperature Physics - University of Liverpool

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The magnetic refrigerator We have seen that using dilution of helium-3, we could reach temperatures in the milliKelvin range. If we want to go below that, a completely new technology is needed. This can be achieved using magnetic cooling. Historically, magnetic cooling has developed in 2 stages. When it was first proposed in the 1920s, paramagnetic salts was used for cooling. Today, this method can each down to milliKelvin temperatures. The use of paramagnetic salt has now been largely replaced by the dilution refrigerator. In the 1950s, the use of the magnetic moment of nuclei in metals was started. This method can now reach microKelvin temperatures. Whether it is magnetic moments of electrons in salts or nuclei in metals, the principle is the same. Statistical Physics 3 Oct - Dec 2009
9.1 The Principle of Magnetic Cooling Statistical Physics 4 Oct - Dec 2009
Page 1 and 2: Statistical and Low Temperature Phy
Page 3: Sections The magnetic refrigerator
Page 7 and 8: The Principle of Magnetic Cooling T
Page 9 and 10: The Principle of Magnetic Cooling A
Page 11 and 12: The Principle of Magnetic Cooling N
Page 13 and 14: The Principle of Magnetic Cooling P
Page 15 and 16: How does it work? We have seen how
Page 17 and 18: An adiabatic, constant entropy chan
Page 19 and 20: 9.2 Thermodynamics of Magnetic Cool
Page 21 and 22: Thermodynamics of Magnetic Cooling
Page 25 and 26: The new temperature is Thermodynami
Page 31 and 32: Interaction between magnetic dipole
Page 33 and 34: Interaction between magnetic dipole
Page 35 and 36: Magnetic disorder entropy Previousl
Page 37 and 38: Magnetic disorder entropy Substitut
Page 39 and 40: Magnetic disorder entropy The expan
Page 41 and 42: Magnetic Refrigerators The performa
Page 43 and 44: Magnetic Refrigerators The follow g
Page 45 and 46: Magnetic Refrigerators These are ex
Page 47 and 48: 9.6 Nuclear Refrigeration Statistic
Page 49 and 50: Nuclear Refrigeration To get some i
Page 51 and 52: Nuclear Refrigeration From the entr
Page 53 and 54: Nuclear Refrigeration Because the s
Page 55 and 56:
Nuclear Refrigeration One disadvant
Page 57 and 58:
Nuclear Refrigeration The copper bl
Page 59 and 60:
Nuclear Refrigeration The copper bl
Page 61 and 62:
Nuclear Refrigeration The small nuc
Page 63 and 64:
From the entropy formula, Nuclear R
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Nuclear Refrigeration To see how we
Page 67 and 68:
Nuclear Refrigeration The other way
Page 69 and 70:
Nuclear Refrigeration Note that usi
Page 71 and 72:
Nuclear Refrigeration (a) The nucle
Page 73 and 74:
Nuclear Refrigeration Notice from t
Page 75 and 76:
9.7 Exercises Statistical Physics 7
Page 77 and 78:
Define Exercises x = µ BB k BT . R
Page 79 and 80:
Exercise 2 Exercises CMN is a spin-
Page 81 and 82:
Exercises where C is the heat capac
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Exercises The entropy change refers
Page 85 and 86:
Exercises A spin 1/2 salt would hav
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Exercise 4 Exercises At which nucle
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Exercise 5 Exercises How long would
Page 91 and 92:
Exercises We also need to assume th
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n = 20, B = 8 T, Ti = 0.015 K and n
Page 95:
then Exercises nλnB 2 ∆Q = T ∆
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Statistical and Low Temperature Physics - University of Liverpool

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