Statistical and Low Temperature Physics - University of Liverpool

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The Principle of Magnetic Cooling Consider a paramagnetic salt. This salt contains ions with magnetic moments coming from their electrons. At mK temperatures, the magnetic disorder entropy (about 1 J/mol) is large compared to all other entropies, such as lattice and coduction electron entropies, which may be neglected. We have previously looked at the properties of a paramagnetic salt. The entropy would be a function of the magnetic field applied. We shall look at the derivation of the entropy formula later. First, we look at the known behaviour of the entropy and see how this can help us to understand magnetic cooling. Statistical Physics 5 Oct - Dec 2009
The Principle of Magnetic Cooling This graph show the entropy against temperature for a commonly used paramagnetic salt. S.A.J. Wiegers, P.E.Wolf, L. Puech: Physica B 165 & 166, 165 (1990) We start by familiarising ourselves with the various features of the graph. Statistical Physics 6 Oct - Dec 2009
Page 1 and 2: Statistical and Low Temperature Phy
Page 3 and 4: Sections The magnetic refrigerator
Page 5: 9.1 The Principle of Magnetic Cooli
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
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Nuclear Refrigeration The copper bl
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Nuclear Refrigeration The copper bl
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Nuclear Refrigeration The small nuc
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From the entropy formula, Nuclear R
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Nuclear Refrigeration To see how we
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Nuclear Refrigeration The other way
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Nuclear Refrigeration Note that usi
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Nuclear Refrigeration (a) The nucle
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Nuclear Refrigeration Notice from t
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9.7 Exercises Statistical Physics 7
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Define Exercises x = µ BB k BT . R
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Exercise 2 Exercises CMN is a spin-
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Exercises where C is the heat capac
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Exercises The entropy change refers
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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
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Exercises We also need to assume th
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n = 20, B = 8 T, Ti = 0.015 K and n
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then Exercises nλnB 2 ∆Q = T ∆
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Statistical and Low Temperature Physics - University of Liverpool

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