Glassy dynamics in CuMn thin-film multilayers

Journal Article · Mon Feb 06 00:00:00 EST 2017 · Physical Review B

DOI:https://doi.org/10.1103/PhysRevB.95.054304· OSTI ID:1594050

Zhai, Qiang ^[1]; Harrison, David C. ^[2]; Tennant, Daniel ^[1]; Dahlberg, E. Dan ^[2]; Kenning, Gregory G. ^[3]; Orbach, Raymond L. ^[1]

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1. Univ. of Texas, Austin, TX (United States). Texas Materials Inst. (TMI)
2. Univ. of Minnesota, Minneapolis, MN (United States)
3. Indiana Univ. of Pennsylvania, Indiana, PA (United States)

Thin-film multilayered spin-glass CuMn/Cu structures exhibit glassy dynamics. The freezing temperature $T_f$ was measured for 40 layers of CuMn films of thickness $\mathcal{L}=4.5,9.0$, and 20.0 nm, sandwiched between nonmagnetic Cu layers of thickness $\approx 60$ nm. The Kenning effect, $T_f\propto ln\mathcal{L}$, is shown to follow from power-law dynamics where the correlation length grows from nucleation as $\xi (t,T)=c_1{a}_0{(t/{\tau }_0)}^{c_2(T/T_g)}$, leading to $[(T_f/T_g)c_{2}ln(t_{\text{co}}/{\tau }_0)]+ln{c}_1=ln(\mathcal{L}/a_0)$. Here, $T_g$ is the bulk spin-glass temperature, $c_1$ and $c_2$ are constants determined from the spin-glass dynamics, $t_{\text{co}}$ is the time for the correlation length to grow to the film thickness, ${\tau }_0$ is a characteristic exchange time $\approx \hslash /k_B{T}_g$, and $a_0$ is the average Mn-Mn separation. For $t\ge t_{\text{co}}$, the magnetization dynamics are simple activated, with a single activation energy ${\mathrm{\Delta }}_{\text{max}}\left(\mathcal{L}\right)/k_B{T}_g=(1/c_2)[ln(\mathcal{L}/a_0)-ln{c}_1]$ that does not change with time. Values for all these parameters are found for the three values of $\mathcal{L}$ explored in these measurements. We find experimentally ${\mathrm{\Delta }}_{\text{max}}\left(\mathcal{L}\right)/k_B=907$, 1246, and 1650 K, respectively, for the three CuMn thin-film multilayer thicknesses, consistent with power-law dynamics. Here, we perform a similar analysis based on the activated dynamics of the droplet model and find a much larger spread for ${\mathrm{\Delta }}_{\text{max}}\left(\mathcal{L}\right)$ than found experimentally.

• Research Organization: Univ. of Texas, Austin, TX (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES)
• Grant/Contract Number: SC0013599
• OSTI ID: 1594050
• Alternate ID(s): OSTI ID: 1342810
• Journal Information: Physical Review B, Vol. 95, Issue 5; ISSN 2469-9950
• Publisher: American Physical Society (APS)
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
spin glasses
correlation lengths
dynamical systems