We shall present our studies on various magnetic glasses including - PowerPoint PPT Presentation

Glass-like arrested states across 1 st order magnetic transitions P. Chaddah UGC-DAE Consortium for Scientific Research, Indore. We shall present our studies on various magnetic glasses including CMR manganites and magnetic shape-memory alloys. We have exploited the magnetic field as a second control variable to create and use new measurement protocols that may have analogies for structural glasses [1]. [1] P. Chaddah and A. Banerjee, arXiv:1107.0125 , and references therein

Study of 1 st Order transitions using magnetic field larger variation of T C with the experimentally available range of H than with the experimentally available range of P.

Signatures of 1 st Order transitions 1 st Order Transition allows Supercooling/Superheating Free Energy T C Temperature No Limits for supercooling or superheating?

P T T cr PV Isotherms Vanderwaal s gas T 1 P * - Limit of Supercooling of Gas P ** - Limit of Superheating of Liq P * P C1 T 2 <T 1 P C1 P ** P * P C2 P C2 P ** V Supercooling/Superheating & hysteresis

Across a 1 st Order transition, one can Supercool the liquid (disordered state) or Superheat the solid (ordered state)  Observe hysteresis, supercooling. Form a Glass (arrest the kinetics) Glass is time held still  disorder can be other than structural Magnetic Glass  a glass-like arrested state A glass-like arrested state is formed when we succeed in cooling across a 1 st order transition while extracting the specific heat but without extracting the latent heat.

Barrier falls as one cools from T C to T*, and relaxation rate will rise.

Giles Tarjus

With disorder broadening Chaddah Pramana-J Phys 67 (2006) CHUF (cooling & heating in unequal fields)

Magnetization Measurements on Ni 50 Mn 35 Sn 15 Ribbon (prepared by Melt spinning) 0 .0 5 T 7 0 N i 50 M n 35 S n 15 1 .5 T 6 5 9 T 6 0 5 5 5 0 M(emu/gm) 4 5 4 0 3 5 3 0 2 5 2 0 0 5 0 1 0 0 1 5 0 2 0 0 2 5 0 3 0 0 3 5 0 4 0 0 T (K ) Alok Banerjee, S Dash, Archana Lakhani, Ramanujan et al

A M A M A M T * T C T**

80 M s FCC Ni 45 Co 5 Mn 38 Sn 12 FCW 70 H = 0.05T 60 A f M (emu/g) 50 40 M f 30 A s 0 50 100 150 200 250 300 350 T ( K ) Alok Banerjee, S Dash, Archana Lakhani, Prof Ramanujan et al

Ni 45 Co 5 Mn 38 Sn 12 Ribbon XRD 7000 6000 6000 300K 300K 5000 4800 4000 3600 I(AU) I(AU) 3000 2400 2000 1200 1000 0 0 6000 20 30 40 50 60 70 80 6000 41.0 41.5 42.0 42.5 43.0 43.5 44.0 44.5 45.0 4800 150K 4800 150K I(AU) 3600 I(AU) 3600 2400 2400 1200 1200 0 0 2000 20 30 40 50 60 70 80 41.0 41.5 42.0 42.5 43.0 43.5 44.0 44.5 45.0 90K 1500 1400 90K I(AU) I(AU) 1000 700 500 0 0 20 30 40 50 60 70 80 41 42 43 44 45 2  2  N P Lalla et al

Intensity vs. Temperature plot for Austenite and Martensite peak height in Ni 45 Co 5 Mn 38 Sn 12 9000 8000 7000 6000 Intensity (AU) 5000 4000 Cooling- Austenite peak Heating- Austenite peak Cooling- Marteniste peak 3000 Heating- Martensite peak 2000 1000 0 50 100 150 200 250 300 T(K) N P Lalla et al

Can measure thru structure  both crystal & magnetic  Both X-ray and neutron diffrcn.

Magnetization Measurements on Ni 50 Mn 35 Sn 15 Ribbon (prepared by Melt spinning) 0 .0 5 T 7 0 N i 50 M n 35 S n 15 1 .5 T 6 5 9 T 6 0 5 5 5 0 M(emu/gm) 4 5 4 0 3 5 3 0 2 5 2 0 0 5 0 1 0 0 1 5 0 2 0 0 2 5 0 3 0 0 3 5 0 4 0 0 T (K ) Alok Banerjee, S Dash, Archana Lakhani, Ramanujan et al

T ( K ) T ( K ) 0 50 100 150 200 250 300 0 40 80 120 160 200 3.2 3 Measured in 1T Measured in 3T while warm ing while warm ing C ooled in 6T 2.4 C ooled in 3T 2 C ooled in 6T M (  B / f.u. ) M (  B / f.u ) C ooled in 1T C ooled in 4T C ooled in 0T C ooled in 3T 1.6 1 (a) 0.8 0 1.0 Measured in 3T M easured in 1T 2.5 while warm ing while warm ing 0.9 M (  B / f.u. ) M (  B / f.u ) 2.0 C ooled in 6T 0.8 C ooled in 6T C ooled in 4T C ooled in 3T C ooled in 3T 1 C ooled in 1T 1 0.7 1.5 0.6 (b) 1.0 2 2 35 40 45 50 55 60 65 70 30 40 50 60 70 80 T ( K ) At same (T,H) we get different T ( K ) values of M depending on the history. At same (T,H,M) we get Alok Banerjee different .

Water shows supercooling, superheating, glass state & Mpemba effect!!

Does hot water freeze first? - physicsworld.com Does hot water freeze first? Mar 29, 2006 Since the time of Aristotle, some scientists have claimed that hot water freezes faster than cold. Philip Ball looks at current attempts to shed light on this puzzling phenomenon. It sounds like the kind of question you would be dismayed to hear schoolchildren getting wrong: which takes less time to freeze, cold or hot water? Common sense and the laws of thermodynamics appear to insist that cold water must freeze first.

Measured in 3T 2.0 1 37.5 K 1.9 M (  B / f.u. ) 1.8 2 Cooled in 6T Cooled in 4T Cooled in 3.85T 1.7 100 500 1000 5000 10000 50000 t ( sec ) Overtaking, while approaching equilibrium Chaddah et al arXiv.org:1011.3598

Overtaking, while approaching equilibrium 0.63 Measured in 1T t (sec) 0 3600 7200 10800 14400 18000 21600 0.62 0.80 52.5 K Measured in 1T 40.5 K M (  B / f.u. ) 0.78 0.61 Cooled in 6T Cooled in 3T M (  B / f.u. ) 0.76 0.60 Cooled in 6T Cooled in 1T 0.74 0.58 0.72 (a) 100 1000 10000 t ( sec ) 0.61 Measured in 1T 1.3 0.60 Measured in 3T 56 K M (  B / f.u. ) 0.59 Cooled in 6T 52 K Cooled in 1T 0.58 M (  B / f.u. ) 0.57 1.2 0.56 (b) 0 3600 7200 10800 14400 18000 21600 Cooled in 6T t (sec) Cooled in 3T 100 1000 10000 Chaddah et al arXiv.org:1011.3598 t (sec)

Overtaking, while approaching equilibrium M (  B / f. u. ) 52K M (  B / f. u. ) 100 1000 10000 t ( sec ) Cooled in 6T Cooled in 2.9T Measured in 3T 100 1000 10000 t ( sec ) Chaddah et al arXiv.org:1011.3598

A second control variable , other than temperature, will help understand glass physics . Magnetic field is a good control variable (cf pressure) . CHUF, a new protocol to study g lass- l ike a rrested s tates

Vision Statement To see what others have seen, but .. To think what others have not thought. To pursue those new thoughts, and then To see what others have not seen.

used all 3 (kinetic arrest, magnetic glass, CHUF) keywords

They used all 3 keywords (kinetic arrest, magnetic glass, CHUF) multiple times each. Referred only once!! Praised the CHUF protocol, which is based on a new understanding of the physical process involved.

arXiv:1201.5255

1108.4117 Both H & P together JPCM( in press)

1108.4117 Both H & P together JPCM(in press)