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

Glass-like arrested states across 1st 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 1st Order transitions using magnetic field

larger variation of TC with the experimentally available range of H than with the experimentally available range of P.

Free Energy Temperature

1st Order Transition allows Supercooling/Superheating TC

No Limits for supercooling or superheating?

Signatures of 1st Order transitions

PC1

V P

PV Isotherms Vanderwaal s gas P* - Limit of Supercooling of Gas P** - Limit of Superheating of Liq P* T Tcr

PC1 T1 T2<T1 PC2 PC2

P* P** P** Supercooling/Superheating & hysteresis

Across a 1st 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 1st order transition while extracting the specific heat but without extracting the latent heat.

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

Giles Tarjus

Chaddah Pramana-J Phys 67 (2006)

CHUF (cooling & heating in unequal fields)

With disorder broadening

Magnetization Measurements on Ni50Mn35Sn15 Ribbon (prepared by Melt spinning)

5 0 1 0 0 1 5 0 2 0 0 2 5 0 3 0 0 3 5 0 4 0 0 2 0 2 5 3 0 3 5 4 0 4 5 5 0 5 5 6 0 6 5 7 0

M(emu/gm) T (K )

0 .0 5 T 1 .5 T 9 T N i50M n 35S n 15

Alok Banerjee, S Dash, Archana Lakhani, Ramanujan et al

T * TC T** M A M A M A

50 100 150 200 250 300 350 30 40 50 60 70 80

M (emu/g) T ( K ) FCC FCW H = 0.05T

Ms

Af

As Mf Ni45Co5Mn38Sn12

Alok Banerjee, S Dash, Archana Lakhani, Prof Ramanujan et al

1000 2000 3000 4000 5000 6000 7000

1200 2400 3600 4800 6000

41 42 43 44 45

500 1000 1500 2000

I(AU)

300K

I(AU)

150K

I(AU)

2

90K

1200 2400 3600 4800 6000

1200 2400 3600 4800 6000

20 30 40 50 60 70 80

700 1400

I(AU)

300K

I(AU)

150K

I(AU)

2

90K

Ni45Co5Mn38Sn12 Ribbon XRD

N P Lalla et al

50 100 150 200 250 300 1000 2000 3000 4000 5000 6000 7000 8000 9000 Cooling- Austenite peak Heating- Austenite peak Cooling- Marteniste peak Heating- Martensite peak

Intensity (AU) T(K)

Intensity vs. Temperature plot for Austenite and Martensite peak height in Ni45Co5Mn38Sn12

N P Lalla et al

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

Magnetization Measurements on Ni50Mn35Sn15 Ribbon (prepared by Melt spinning)

5 0 1 0 0 1 5 0 2 0 0 2 5 0 3 0 0 3 5 0 4 0 0 2 0 2 5 3 0 3 5 4 0 4 5 5 0 5 5 6 0 6 5 7 0

M(emu/gm) T (K )

0 .0 5 T 1 .5 T 9 T N i50M n 35S n 15

Alok Banerjee, S Dash, Archana Lakhani, Ramanujan et al

0.8 1.6 2.4 3.2 40 80 120 160 200 30 40 50 60 70 80 1.0 1.5 2.0 2.5 T ( K )

Measured in 3T while warm ing

M ( B / f.u. )

C ooled in 6T C ooled in 4T C ooled in 3T

1 2

C ooled in 6T C ooled in 4T C ooled in 3T

M ( B / f.u. ) T ( K )

Measured in 3T while warm ing

1 2 3 50 100 150 200 250 300 35 40 45 50 55 60 65 70 0.6 0.7 0.8 0.9 1.0 T ( K )

(a)

Measured in 1T while warm ing

M ( B / f.u )

C ooled in 6T C ooled in 3T C ooled in 1T C ooled in 0T

2 1

(b)

T ( K ) M ( B / f.u )

M easured in 1T while warm ing C ooled in 6T C ooled in 3T C ooled in 1T

Alok Banerjee At same (T,H) we get different values of M depending on the

• history. At same (T,H,M) we get

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.

100 500 1000 5000 10000 50000

1.7 1.8 1.9 2.0 2 1

37.5 K Measured in 3T

M ( B / f.u. ) t ( sec )

Cooled in 6T Cooled in 4T Cooled in 3.85T

Overtaking, while approaching equilibrium

Chaddah et al arXiv.org:1011.3598

0.72 0.74 0.76 0.78 0.80

3600 7200 10800 14400 18000 21600 3600 7200 10800 14400 18000 21600

0.56 0.57 0.58 0.59 0.60 0.61 Measured in 1T

(a)

t (sec) 40.5 K M ( B / f.u. ) Cooled in 6T Cooled in 3T 56 K Measured in 1T

(b)

Cooled in 6T Cooled in 1T M ( B / f.u. ) t (sec)

100 1000 10000 0.58 0.60 0.61 0.62 0.63

Measured in 1T 52.5 K

M ( B / f.u. ) t ( sec )

Cooled in 6T Cooled in 1T

100 1000 10000 1.2 1.3

52 K Measured in 3T

M ( B / f.u. ) t (sec) Cooled in 6T Cooled in 3T

Chaddah et al arXiv.org:1011.3598

Overtaking, while approaching equilibrium

100 1000 10000

100 1000 10000

52K

Measured in 3T

M ( B / f. u. ) t ( sec )

Cooled in 6T Cooled in 2.9T

M ( B / f. u. )

t ( sec )

Overtaking, while approaching equilibrium

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 glass-like

arrested states

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.

Vision Statement

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

1108.4117Both H & P together

JPCM( in press)

1108.4117Both H & P together

JPCM(in press)